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43.7A: Gestacija čovjeka - biologija

43.7A: Gestacija čovjeka - biologija



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Nakon što se zigota usadi u stijenku maternice, razvoj embrija i fetusa nastavlja se kroz tri tromjesečja do rođenja.

ciljevi učenja

  • Opišite razvoj ljudskog fetusa od oplodnje do trećeg tromjesečja

Ključne točke

  • Nakon oplodnje, zigota se implantira u stijenku maternice; njegov vanjski sloj raste u endometrij, gdje počinje proizvoditi humani korionski gonadotropin.
  • Tijekom prvog tromjesečja posteljica se formira zajedno s unutarnjim organima i strukturama; međutim, u ovom trenutku ne funkcioniraju svi unutarnji organi.
  • Tijekom drugog tromjesečja, unutarnji organi nastavljaju se razvijati i fetus postaje aktivan.
  • Treće tromjesečje je brzog rasta u kojem fetus dostiže svoju punu veličinu; trudnoća često postaje neugodna za majku.

Ključni uvjeti

  • zigota: diploidna oplođena jajna stanica
  • korion: omogućuje izmjenu kisika i ugljičnog dioksida između embrija i vanjskog okruženja jaja
  • humani korionski gonadotropin: peptidni hormon, proizveden tijekom trudnoće, koji sprječava razgradnju žutog tijela i održava proizvodnju progesterona
  • posteljica: vaskularni organ u sisavaca koji opskrbljuje hranu i kisik od majke do fetusa, dok vraća otpad; implantira se u stijenku maternice

Ljudska trudnoća

Dvadeset četiri sata prije oplodnje, jajašce je završilo mejozu i postalo zreli oocit. Kad se oplodi (pri začeću), jajna stanica, sada poznata kao zigota, putuje kroz jajovod do maternice. Embrij u razvoju mora se implantirati u stijenku maternice u roku od sedam dana ili će se pogoršati i umrijeti. Vanjski slojevi zigote (blastociste) rastu u endometrij probavljanjem stanica endometrija. Zacjeljivanje rana endometrija zatvara blastocitu u tkivo. Drugi sloj blastociste, korion, počinje oslobađati hormon koji se naziva humani korionski gonadotropin (hCG) koji se probija do žutog tijela, održavajući ga aktivnim. Time se osigurava odgovarajuća razina progesterona koji će održavati endometrij maternice za potporu razvoju embrija. Testovi trudnoće određuju razinu hCG -a u urinu ili serumu: ako je prisutan hormon, test je pozitivan.

Prvo tromjesečje

Razdoblje trudnoće podijeljeno je u tri jednaka razdoblja ili tromjesečja. Tijekom prva dva do četiri tjedna prvog tromjesečja, endometrija sluznica se hrani pomoću hrane i otpada putem difuzije. Kako tromjesečje napreduje, vanjski sloj embrija počinje se spajati s endometrijem i formira se posteljica. Ovaj organ preuzima potrebe za hranjivim tvarima i otpadom embrija i fetusa, a majčina krv prenosi hranjive tvari u posteljicu i uklanja otpad iz nje. Kemikalije iz fetusa, poput bilirubina, majčina jetra obrađuje radi eliminacije. Neki od majčinih imunoglobulina proći će kroz placentu, pružajući pasivni imunitet protiv nekih potencijalnih infekcija.

Unutarnji organi i tjelesne strukture počinju se razvijati tijekom prvog tromjesečja. Do pet tjedana u osnovi su formirani pupoljci udova, oči, srce i jetra. Do osam tjedana primjenjuje se izraz fetus; tijelo je u biti formirano. Pojedinac je dugačak oko pet centimetara i mnogi organi, poput pluća i jetre, još ne funkcioniraju. Izlaganje bilo kojim otrovima posebno je opasno tijekom prvog tromjesečja jer svi tjelesni organi i strukture prolaze početni razvoj. Sve što utječe na taj razvoj može imati ozbiljan utjecaj na opstanak fetusa.

Drugo tromjesečje

Tijekom drugog tromjesečja, fetus naraste do oko 30 cm (12 inča). Kako postaje aktivna, majka obično osjeća prve pokrete. Svi organi i strukture nastavljaju se razvijati. Posteljica je preuzela funkcije prehrane i otpada, zajedno s proizvodnjom estrogena i progesterona iz žutog tijela koje se degeneriralo. Posteljica će nastaviti funkcionirati kroz porođaj.

Treće tromjesečje

Tijekom trećeg tromjesečja, fetus naraste do 3 do 4 kg (6 ½ -8 ½ lbs.) I dug oko 50 cm (19-20 inča). Ovo je razdoblje najbržeg rasta tijekom trudnoće. Razvoj organa nastavlja se rađati (a neki sustavi, poput živčanog sustava i jetre, nastavljaju se razvijati i nakon rođenja). Majka će biti najneugodnija tijekom ovog tromjesečja. Može učestalo mokriti zbog pritiska fetusa na mjehur. Također može doći do začepljenja crijeva i problema s cirkulacijom, osobito u nogama. U nogama se mogu stvoriti ugrušci zbog pritiska fetusa na povratne vene pri ulasku u trbušnu šupljinu.


Gestacija

Naši urednici će pregledati ono što ste podnijeli i odlučiti trebate li izmijeniti članak.

Gestacija, kod sisavaca, vrijeme između začeća i rođenja, tijekom kojeg se embrij ili fetus razvijaju u maternici. Ova definicija izaziva povremene poteškoće jer se kod nekih vrsta (npr. Majmuna i čovjeka) ne može znati točno vrijeme začeća. U tim slučajevima početak gestacije obično se datira s neke dobro definirane točke reproduktivnog ciklusa (npr. S početkom prethodne menstruacije).

Duljina trudnoće varira od vrste do vrste. Najkraća poznata trudnoća je virginijski oposum, oko 12 dana, a najduža indijska slonova, oko 22 mjeseca. Tijekom evolucije trajanje trudnoće prilagođeno je potrebama vrste. Stupanj konačnog rasta faktor je, manje životinje obično imaju kraća razdoblja trudnoće od većih. Izuzetak su zamorci i srodni južnoamerički glodavci, kod kojih je gestacija produžena (u prosjeku 68 dana za zamorca i 111 dana za činčilu). Mladunci ovih vrsta rođeni su u stanju veće zrelosti nego oni štakora s razdobljem od 22 dana. Drugi je faktor da se kod mnogih vrsta s ograničenom sezonom razmnožavanja gestacija prilagođava tako da se rođenje poklapa s razdobljem u kojem hrane ima najviše. Tako konj, proljetni uzgajivač s 11 mjeseci gestacije, slijedećeg proljeća dobiva mlade, kao i ovce, uzgajivač jeseni s pet mjeseci trudnoće. Životinje koje žive na otvorenom imaju dulju gestaciju i rađaju mlade koji su dosegli stanje veće zrelosti nego životinje koje mogu sakriti svoje mlade u podzemnim rupama ili u špiljama. Torbari općenito imaju kratku trudnoću - npr. 40 dana za najveće klokane. Mladi, rođeni u izrazito nezrelom stanju, premještaju se u vrećicu u kojoj se može reći da će se trudnoća nastaviti.

Zametci nekih vrsta doživljavaju zastoj u razvoju koji uvelike produljuje trudnoću. To se posebno odnosi na mesoždere krznare kune i lasice. Zametci europskog jazavca i američke kune, koji se razmnožavaju u srpnju i kolovozu, razvijaju se nekoliko dana, a zatim leže uspavani u maternici, a implantiraju se u siječnju. Rođenje se događa u ožujku. Od ukupnog razdoblja trudnoće od 250 dana, rast se javlja tijekom samo 50. Do odgođene implantacije dolazi i kod miševa i drugih malih glodavaca koji zatrudne dok još sisaju leglo.

Bilo jedan faktor ili veliki broj manjih čimbenika, koji kulminiraju na ili blizu jednog datuma, određuju duljinu trudnoće. Poznato je nekoliko manjih varijacija: kod muškaraca je trudnoća za mužjake tri do četiri dana dulja od one za ženke, a kod goveda bikovi se nose oko jedan dan dulje od junica. U obje vrste gestacija blizanaca je pet do šest dana manja nego u samca. Kod životinja kao što su zec ili svinja, koje odjednom nose mnogo mladih, gestacija je kraća za veća legla nego za manja. Nasljednost također utječe na gestaciju kod goveda. Prosječno razdoblje trudnoće za holštajn-frizijce iznosi 279 dana za smeđe švicarce, 290 dana ostale pasmine padaju između ovih ekstrema. Kada se hibridi proizvode križanjem dviju vrsta s različitim razdobljima gestacije, hibrid se nosi u razdoblju koje se nalazi negdje između onih dva roditelja i teži majčinoj vrsti. Tako kobila nosi ždrijebe mazge (čiji je otac jarac) otprilike 10 dana duže od normalnog razdoblja za konja (oko 337 dana). Za ljudsku trudnoću, vidjeti trudnoća.


43.7A: Gestacija čovjeka - biologija

Trudnoća počinje oplodnjom jajne stanice i nastavlja se do rođenja jedinke. Duljina gestacije varira među životinjama, ali je vrlo slična među velikim majmunima: gestacija čovjeka je 266 dana, dok je gestacija čimpanze 237 dana, gorila 257 dana, a trudnoća orangutana 260 dana. Lisica ima trudnoću od 57 dana. Psi i mačke imaju sličnu trudnoću u prosjeku 60 dana. Najduža gestacija kopnenih sisavaca je afrički slon sa 640 dana. Najduža gestacija među morskim sisavcima su beluga i kitovi s 460 dana.

Ljudska trudnoća

Dvadeset četiri sata prije oplodnje, jajašce je završilo mejozu i postaje zreli oocit. Kad se oplodi (pri začeću) jajna stanica postaje poznata kao zigota. Zigota putuje kroz jajovod do maternice ((slika)). Embrij u razvoju mora se implantirati u stijenku maternice u roku od sedam dana ili će se pogoršati i umrijeti. Vanjski slojevi zigote (blastociste) urastaju u endometrij probavljanjem stanica endometrija, a zacjeljivanje rana endometrija zatvara blastocistu u tkivo. Drugi sloj blastociste, korion, počinje oslobađati hormon koji se naziva humani beta -korionski gonadotropin (β-HCG) koji se probija do žutog tijela i održava tu strukturu aktivnom. Time se osigurava odgovarajuća razina progesterona koji će održavati endometrij maternice za potporu razvoju embrija. Testovi na trudnoću određuju razinu β-HCG u urinu ili serumu. Ako je prisutan hormon, test je pozitivan.

Slika 1. U ljudi se oplodnja događa ubrzo nakon što oocit napusti jajnik. Implantacija se događa osam ili devet dana kasnije. (Zasluga: Ed Uthman)

Razdoblje trudnoće podijeljeno je u tri jednaka razdoblja ili tromjesečja. Tijekom prva dva do četiri tjedna prvog tromjesečja, endometrija sluznica se hrani pomoću hrane i otpada putem difuzije. Kako tromjesečje napreduje, vanjski sloj embrija počinje se stapati s endometrijem, a formira se posteljica. Ovaj organ preuzima potrebe za hranjivim tvarima i otpadom embrija i fetusa, a majčina krv prenosi hranjive tvari u posteljicu i uklanja otpad iz nje. Kemikalije iz fetusa, poput bilirubina, majčina jetra obrađuje radi eliminacije. Neki od majčinih imunoglobulina proći će kroz placentu, pružajući pasivni imunitet protiv nekih potencijalnih infekcija.

Unutarnji organi i tjelesne strukture počinju se razvijati tijekom prvog tromjesečja. Do pet tjedana u osnovi su formirani pupoljci udova, oči, srce i jetra. Do osam tjedana primjenjuje se izraz fetus, a tijelo je u biti formirano, kao što je prikazano na (slika). Pojedinac je dugačak oko pet centimetara, a mnogi organi, poput pluća i jetre, još ne funkcioniraju. Izlaganje bilo kojim otrovima posebno je opasno tijekom prvog tromjesečja jer svi tjelesni organi i strukture prolaze početni razvoj. Sve što utječe na taj razvoj može imati ozbiljan utjecaj na opstanak fetusa.

Slika 2. Fetalni razvoj se pokazuje u devet tjedana trudnoće. (zasluga: Ed Uthman)

Tijekom drugog tromjesečja, fetus naraste do oko 30 cm (12 inča), kao što je prikazano na (slika). Postaje aktivna i majka obično osjeća prve pokrete. Svi organi i strukture nastavljaju se razvijati. Posteljica je preuzela funkcije prehrane i otpada te proizvodnju estrogena i progesterona iz žutog tijela koje se degeneriralo. Posteljica će nastaviti funkcionirati tijekom poroda.

Slika 3. Ovaj fetus tek ulazi u drugo tromjesečje, kada posteljica preuzima više funkcija koje se obavljaju tijekom razvoja djeteta. (kredit: Nacionalni muzej zdravlja i medicine)

Tijekom trećeg tromjesečja, fetus naraste do 3 do 4 kg (6 ½ -8 ½ lbs.) I dugačak oko 50 cm (19-20 inča), kako je prikazano na (slika). Ovo je razdoblje najbržeg rasta tijekom trudnoće. Razvoj organa nastavlja se rađati (a neki sustavi, poput živčanog sustava i jetre, nastavljaju se razvijati i nakon rođenja). Majka će biti najneugodnija tijekom ovog tromjesečja. Može učestalo mokriti zbog pritiska fetusa na mjehur. Također može doći do začepljenja crijeva i problema s cirkulacijom, osobito u nogama. U nogama se mogu stvoriti ugrušci zbog pritiska fetusa na povratne vene pri ulasku u trbušnu šupljinu.

Slika 4. Tijekom trećeg tromjesečja dolazi do brzog rasta fetusa. (zasluga: izmjena djela prema Grey's Anatomy)

Porod i rad

Porod je fizički napor izbacivanja fetusa i posteljice iz maternice tijekom poroda (porod). Pred kraj trećeg tromjesečja estrogen uzrokuje razvoj receptora na stijenci maternice i vezanje hormona oksitocina. U to se vrijeme dijete preusmjerava, okrenuto prema naprijed i prema dolje sa stražnjom ili tjemenom glave zahvaćajući grlić maternice (otvor maternice). Zbog toga se vrat maternice rasteže, a živčani impulsi šalju se u hipotalamus, koji signalizira oslobađanje oksitocina iz stražnje hipofize. Oksitocin uzrokuje kontrakciju glatkih mišića u stijenci maternice. Istodobno, posteljica oslobađa prostaglandine u maternicu, povećavajući kontrakcije. Relej pozitivne povratne informacije javlja se između maternice, hipotalamusa i stražnje hipofize kako bi se osigurala odgovarajuća opskrba oksitocinom. Kako se regrutira više stanica glatkih mišića, kontrakcije povećavaju intenzitet i snagu.

Postoje tri faze porođaja. Tijekom prve faze cerviks se tanji i širi. To je potrebno kako bi se beba i posteljica izbacili tijekom rođenja. Vrat maternice će se na kraju proširiti na oko 10 cm. Tijekom druge faze, dijete je izbačeno iz maternice. Maternica se steže, a majka gura dok sabija trbušne mišiće kako bi pomogla porodu. Posljednja faza je prolazak posteljice nakon rođenja djeteta i potpunog odvajanja organa od stijenke maternice. Ako bi porod trebao prestati prije nego što se dostigne druga faza, može se primijeniti sintetski oksitocin, poznat kao Pitocin, za ponovno pokretanje i održavanje poroda.

Alternativa trudu i porodu je kirurški porođaj djeteta putem postupka koji se naziva carskim rezom. Ovo je velika abdominalna operacija i može dovesti do postoperativnih komplikacija za majku, ali u nekim slučajevima to može biti jedini način za sigurno rođenje djeteta.

Majčine mliječne žlijezde prolaze kroz promjene tijekom trećeg tromjesečja kako bi se pripremile za dojenje i dojenje. Kad beba počne sisati dojku, signali se šalju u hipotalamus uzrokujući oslobađanje prolaktina iz prednje hipofize. Prolaktin uzrokuje mliječne žlijezde da proizvode mlijeko. Otpušta se i oksitocin koji potiče oslobađanje mlijeka. Mlijeko sadrži hranjive tvari za razvoj i rast djeteta, kao i imunoglobuline za zaštitu djeteta od bakterijskih i virusnih infekcija.

Neplodnost je nemogućnost začeća djeteta ili rođenja djeteta. Može se identificirati oko 75 posto uzroka neplodnosti, uključujući bolesti, poput spolno prenosivih bolesti koje mogu uzrokovati ožiljke na reproduktivnim cijevima bilo kod muškaraca ili žena, ili razvojne probleme koji su često povezani s abnormalnom razinom hormona u jedne od osoba. Neadekvatna prehrana, osobito gladovanje, može odgoditi menstruaciju. Stres također može dovesti do neplodnosti. Kratkoročni stres može utjecati na razinu hormona, dok dugotrajni stres može odgoditi pubertet i uzrokovati rjeđe menstrualne cikluse. Drugi čimbenici koji utječu na plodnost uključuju toksine (poput kadmija), pušenje duhana, upotrebu marihuane, ozljede spolnih žlijezda i starenje.

Ako se utvrdi neplodnost, na raspolaganju je nekoliko tehnologija potpomognute reprodukcije (ART) koje pomažu začeću. Uobičajena vrsta ART -a je in vitro oplodnja (IVF) gdje se jajna stanica i spermatozoidi kombiniraju izvan tijela, a zatim stavljaju u maternicu. Jaja se dobivaju od žene nakon opsežnih hormonskih tretmana koji pripremaju zrela jajašca za oplodnju i pripremaju maternicu za implantaciju oplođene jajne stanice. Spermatozoidi se dobivaju od čovjeka te se kombiniraju s jajima i podržavaju kroz nekoliko dioba stanica kako bi se osigurala održivost zigota. Kad embriji dosegnu osmostanični stadij, jedan ili više njih implantira se u žensku maternicu. Ako se oplodnja ne postiže jednostavnim IVF -om, može se upotrijebiti postupak ubrizgavanja sperme u jajnu stanicu. To se naziva intracitoplazmatska injekcija sperme (ICSI) i prikazano je na (slika). Postupci IVF -a proizvode višak oplođenih jaja i embrija koji se mogu zamrznuti i spremiti za buduću upotrebu. Postupci također mogu rezultirati višestrukim rođenjem.

Slika 5. Spermij je umetnut u jajnu stanicu radi oplodnje tijekom intracitoplazmatske injekcije sperme (ICSI). (zasluga: podaci skale od Matta Russella)


43.7A: Gestacija čovjeka - biologija

Dvadeset četiri sata prije oplodnje, jajašce je završilo mejozu i postaje zreli oocit. Kad se oplodi (pri začeću) jajna stanica postaje poznata kao zigota. Zigota putuje kroz jajovod do maternice (slika 1). Embrij u razvoju mora se implantirati u stijenku maternice u roku od sedam dana ili će se pogoršati i umrijeti. Vanjski slojevi zigote (blastociste) urastaju u endometrij probavljanjem stanica endometrija, a zacjeljivanje rana endometrija zatvara blastocistu u tkivo. Drugi sloj blastociste, korion, počinje oslobađati hormon tzv humani beta -korionski gonadotropin (β-HCG) koji se probija do žutog tijela i održava tu strukturu aktivnom. Time se osigurava odgovarajuća razina progesterona koji će održavati endometrij maternice za potporu razvoju embrija. Testovi na trudnoću određuju razinu β-HCG u urinu ili serumu. Ako je prisutan hormon, test je pozitivan.

Slika 1. U ljudi se oplodnja događa ubrzo nakon što oocit napusti jajnik. Implantacija se događa osam ili devet dana kasnije. (Zasluga: Ed Uthman)

Razdoblje trudnoće podijeljeno je u tri jednaka razdoblja ili tromjesečja. Tijekom prva dva do četiri tjedna prvog tromjesečja, endometrija sluznica se hrani pomoću hrane i otpada putem difuzije. Kako tromjesečje napreduje, vanjski sloj embrija počinje se stapati s endometrijem, a posteljica oblika. Ovaj organ preuzima potrebe za hranjivim tvarima i otpadom embrija i fetusa, a majčina krv prenosi hranjive tvari u posteljicu i uklanja otpad iz nje.

Slika 2. Razvoj ploda prikazan je u devet tjedana trudnoće. (zasluga: Ed Uthman)

Kemikalije iz fetusa, poput bilirubina, majčina jetra obrađuje radi eliminacije. Neki od majčinih imunoglobulina proći će kroz posteljicu, pružajući pasivni imunitet protiv nekih potencijalnih infekcija.

Unutarnji organi i tjelesne strukture počinju se razvijati tijekom prvog tromjesečja. Do pet tjedana u osnovi su formirani pupoljci udova, oči, srce i jetra. Do osam tjedana primjenjuje se izraz fetus, a tijelo je u biti formirano, kao što je prikazano na slici 2.

Pojedinac je dugačak oko pet centimetara i mnogi organi, poput pluća i jetre, još ne funkcioniraju. Izlaganje bilo kojim otrovima posebno je opasno tijekom prvog tromjesečja jer svi tjelesni organi i strukture prolaze početni razvoj. Sve što utječe na taj razvoj može imati ozbiljan utjecaj na opstanak fetusa.

Slika 3. Ovaj fetus tek ulazi u drugo tromjesečje, kada posteljica preuzima više funkcija koje se obavljaju tijekom razvoja djeteta. (kredit: Nacionalni muzej zdravlja i medicine)

Tijekom drugog tromjesečja, fetus naraste do oko 30 cm (12 inča), kao što je prikazano na slici 3. Postaje aktivno i majka obično osjeća prve pokrete. Svi organi i strukture nastavljaju se razvijati.

Posteljica je preuzela funkcije prehrane i otpada te proizvodnju estrogena i progesterona iz žutog tijela koje se degeneriralo. Posteljica će nastaviti funkcionirati tijekom poroda.

Tijekom trećeg tromjesečja, fetus naraste do 3 do 4 kg (6 ½ - 8 ½ lbs.) I dug oko 50 cm (19-20 inča), kako je prikazano na slici 4. To je razdoblje najbržeg rasta tijekom trudnoća. Razvoj organa nastavlja se rađati (a neki sustavi, poput živčanog sustava i jetre, nastavljaju se razvijati i nakon rođenja).

Majka će biti najneugodnija tijekom ovog tromjesečja. Može učestalo mokriti zbog pritiska fetusa na mjehur. Također može doći do začepljenja crijeva i problema s cirkulacijom, osobito u nogama. U nogama se mogu stvoriti ugrušci zbog pritiska fetusa na povratne vene pri ulasku u trbušnu šupljinu.

Slika 4. Postoji brz rast fetusa tijekom trećeg tromjesečja. (zasluga: izmjena djela prema Grey's Anatomy)


Kontracepcija i kontrola rađanja

Prevencija trudnoće potpada pod pojmove kontracepcija ili kontrola rađanja. Strogo govoreći, kontracepcija odnosi se na sprječavanje spajanja spermija i jajašca. Oba pojma se, međutim, često koriste naizmjenično.

Tablica 1. Metode kontracepcije
Metoda Primjeri Stopa grešaka u tipičnoj uporabi tijekom 12 mjeseci
Prepreka muški kondom, ženski kondom, spužva, cervikalna kapa, dijafragma, spermicidi 15 do 24%
Hormonski oralni, flaster, vaginalni prsten 8%
injekcija 3%
implantat manje od 1%
Ostalo prirodno planiranje obitelji 12 do 25%
povlačenje 27%
sterilizacija manje od 1%

Tablica 1 prikazuje uobičajene metode kontracepcije. Navedene stope kvarova nisu idealne stope koje bi se mogle ostvariti, već tipične stope koje se javljaju. Stopa neuspjeha je broj trudnoća koji je posljedica korištenja metode u razdoblju od dvanaest mjeseci. Barijerne metode, poput kondoma, cervikalnih kapa i dijafragmi, blokiraju ulazak spermija u maternicu, sprječavajući oplodnju. Spermicidi su kemikalije koje se stavljaju u rodnicu i ubijaju spermu. Spužve, zasićene spermicidima, stavljaju se u rodnicu na cervikalni otvor. Kombinacijom spermicidnih kemikalija i barijernim metodama postiže se manja stopa neuspjeha nego metode kada se koriste odvojeno.

Gotovo četvrtina parova koji koriste metode barijere, prirodno planiranje obitelji ili povlačenje mogu očekivati ​​neuspjeh metode. Prirodno planiranje obitelji temelji se na praćenju menstrualnog ciklusa i snošaju samo u vrijeme kada jajna stanica nije dostupna. Tjelesna temperatura žene može porasti za stupanj Celzijusa tijekom ovulacije, a cervikalna sluz može povećati volumen i postati podatnija. Ove promjene daju općenitu indikaciju kada će spolni odnos manje ili više rezultirati oplodnjom. Povlačenje uključuje uklanjanje penisa iz rodnice tijekom spolnog odnosa, prije nego što dođe do ejakulacije. Ovo je rizična metoda s velikom stopom neuspjeha zbog moguće prisutnosti spermija u izlučevini bulbourethralne žlijezde, koja može ući u rodnicu prije uklanjanja penisa.

Hormonalne metode koriste sintetski progesteron (ponekad u kombinaciji s estrogenom) kako bi spriječile hipotalamus u oslobađanju FSH ili LH i tako spriječile dostupnost jajašca za oplodnju. Način primjene hormona utječe na stopu neuspjeha. Najpouzdanija metoda, s postotkom neuspjeha manjim od 1 posto, je implantacija hormona pod kožu. Isti stupanj može se postići sterilizacijskim postupcima vazektomije kod muškaraca ili podvezivanjem jajovoda kod žena, ili uporabom intrauterinog uređaja (IUD). IUD se ubacuju u maternicu i uspostavljaju upalno stanje koje sprječava implantaciju oplođenih jajašca u stijenku maternice.

Usklađenost s metodom kontracepcije snažno pridonosi uspjehu ili neuspjehu bilo koje određene metode. Jedina metoda koja je potpuno učinkovita u sprječavanju začeća je apstinencija. Odabir metode kontracepcije ovisi o ciljevima žene ili para. Podvezivanje jajovoda i vazektomija smatraju se trajnom prevencijom, dok su druge metode reverzibilne i pružaju kratkotrajnu kontracepciju.

Prekid postojeće trudnoće može biti spontan ili dobrovoljan. Spontani prekid je pobačaj i obično se javlja vrlo rano u trudnoći, obično unutar prvih nekoliko tjedana. To se događa kada se fetus ne može pravilno razviti i gestacija se prirodno prekida. Dobrovoljni prekid trudnoće je pobačaj. Zakoni koji reguliraju pobačaj razlikuju se među državama i skloni su preživljavanju fetusa smatrati kriterijima za dopuštanje ili sprječavanje postupka.


Trudnoća i porođaj: Kratak pregled biologije i fiziologije

Pregled

Posjedovanje osnovnih znanja i razumijevanje o fizičkim aspektima funkcioniranja tijela u smislu trudnoće i ljudske reprodukcije pružit će studentima temelj za dobro donošenje odluka o njihovom trenutnom i/ili budućem ponašanju u vezi sa spolnim zdravljem. Studenti bi također mogli biti općenito zainteresirani za učenje o stvaranju ljudskog života.

Začeće

Začeće je trenutak oplodnje i povezane promjene koje se događaju u ženskom tijelu koje dovode do ugrađivanja embrija i njegovog rasta unutar maternice. Sljedeći koraci objašnjavaju proces gnojidbe:

Ovulacija je oslobađanje jajašca iz jajnika i najvjerojatnije će se dogoditi sredinom menstrualnog ciklusa, iako se to vrijeme razlikuje među ženkama.

Testisi su mjesto gdje se stvaraju spermije, a epididimis gdje spermatozoidi sazrijevaju.

Vas deferens je uska cijev po kojoj zreli spermiji putuju do prostate.

Prostata stvara tekućinu koja se u kombinaciji sa spermom stvara sjeme tijekom seksualnog uzbuđenja.

Kod žena uzbuđenje uzrokuje da rodnica postane vlažna, što olakšava prihvaćanje uspravnog penisa.

Kod muškaraca, uzbuđenje uzrokuje da se penis napuni krvlju i postane čvrst, što olakšava ulazak u rodnicu.

Kada dođe do vaginalnog spolnog odnosa, oslobađa se mnogo spermija.

Do oplodnje dolazi ako jedan spermatozoid uđe u jajašce u vanjskom dijelu jajovoda.

Oplođeno jaje putuje niz jajovod, ulazi u maternicu i zatim se ugrađuje u sluznicu maternice gdje se hrani i raste.

Oplođeno jaje se naziva zigota i nakon otprilike 30 sati jednostanično oplođeno jaje se dijeli na 2 stanice, zatim na 4, 8 i tako dalje.

Tijekom sljedeća 4 dana višestanični organizam će putovati niz jajovod i ući u maternicu, a zatim će se nekoliko dana kasnije oplođena jajna stanica (sada embrij) pričvrstiti na bogato, zadebljalo tkivo maternice endometrija.

Cijeli proces implantacije obično je dovršen tjedan dana nakon oplodnje.

Trudnoća počinje implantacijom oplođenog jajašca u stijenku maternice, a nakon što se oplođeno jaje usidri, rast i razvoj brzo se ubrzavaju.

Od oplodnje do rođenja potrebno je devet mjeseci.

Faze razvoja tijekom trudnoće

Kralježnica i leđna moždina počinju se razvijati

Oči su razvijene, ali nema kapka

Prvi mali pokreti se dešavaju a majka ih ne osjeća

Udovi, prsti na rukama i nogama se razvijaju

Osjećaju se pokreti fetusa, čuje se otkucaj srca

Spuštena dlaka raste na tijelu

Prisutne su obrve i trepavice, nokti na rukama i nogama

Masnoća se počinje skupljati ispod kože

Na glavi fetusa se razvija dlaka

Po prvi put otvorene oči

Tijelo je prekriveno tvari poput sira

Neke su bebe u ovoj fazi preživjele ako su rođene prerano

Objasnite kako se maternica rasteže dok beba raste. To se može dokazati tako što će učenici stisnuti šaku rukama kako bi ilustrirali približnu veličinu bebe.

Upotrijebite Magno-mate Reproductive Kit iz SRHWA-e (ili druge dolje navedene izvore) za dodatnu podršku za objašnjenje začeća, trudnoće i poroda.

Zdravlje majke tijekom trudnoće

Vrlo je važno da se embriju omogući najbolje moguće okruženje za razvoj, a to znači i dobru prenatalnu skrb za majku, uključujući:

Redoviti odlasci liječniku radi praćenja rasta fetusa i provjere majčinog zdravlja

Lijekovi su potencijalno opasni tijekom trudnoće jer većina kemikalija prolazi kroz placentnu barijeru i utječe na fetus. Alkohol, cigarete i drugi lijekovi mogu negativno utjecati na zdravlje bebe.

Porod i porod

Rad

Porođaj je proces porođaja. Čimbenici koji kontroliraju početak poroda nisu u potpunosti razumljivi.

Otprilike dva tjedna prije stvarnog poroda, dojenče se ‘angažira’, odnosno glava se smješta u zdjelicu spremnu za rođenje.

Trajanje poroda varira od preko 20 sati do samo nekoliko minuta, a na njega mogu utjecati vrsta poroda, dob majke, zdravlje i broj poroda koje je majka ranije imala.

Faze rada

Faza 1- Najduži period porođaja. Kontrakcije maternice uzrokuju progresivno širenje vrata maternice do potpunog otvaranja. Kad se vrat maternice potpuno otvori, amnionska vrećica koja štiti bebu pukne.

Faza 2- Ovo razdoblje može trajati od nekoliko minuta do približno dva sata. Fetus prolazi kroz rodni kanal. Ova faza traje do rođenja djeteta i presijecanja pupčane vrpce.

Faza 3- Obično se završava unutar 10 minuta nakon rođenja djeteta. Posteljica i fetalne membrane izbacuju se nakon rođenja djeteta. Te se strukture nazivaju "naknadnim rođenjem".

Rođenje

Vrste poroda

Spontano - bez umjetne podrške tijekom poroda, spontani porod, bez lijekova.

Pomoć - porođaj se može izazvati probijanjem vode, intravenoznom kapanjem ili gelom koji se stavlja na vrat maternice, lijek za ublažavanje boli može se primijeniti tijekom poroda, alati kao što su pinceta ili ventouse (vakuumski uređaj) mogu se koristiti za pomoć pri porodu.

Carski rez - kada se beba ne može roditi vaginalno, što može biti posljedica različitih razloga povezanih s bebom ili majkom, napravljen je rez u donjem trbušnom zidu i maternici. Beba se vadi kroz rez. Ovaj se postupak provodi pod općom ili regionalnom anestezijom (epiduralnom ili spinalnom).

Majčinski (jednojajčani) blizanci uvijek su istog spola i razvijaju se iz jednog oplođenog jajašca koje se rano u svom razvoju dijeli na dvije polovice.

Bratski (neidentični) blizanci razvijaju se iz dva odvojena oplođena jajašca i nisu slični od samohrane braće i sestara.

Plodnost

Većina parova koji žele zatrudnjeti to čine unutar 12 mjeseci od redovnog (u vrijeme ovulacije) vaginalnog odnosa. Ako se začeće ne dogodi tijekom druge godine, to može biti pokazatelj narušene plodnosti.

Uzroci neplodnosti

Začepljenje jajovoda

Adhezije zdjelice zbog prethodnih spolno prenosivih bolesti, poput klamidije.

Dostupni načini liječenja neplodnosti

Superovulacija i intrauterina oplodnja

Relevantni resursi

Ilustracije

Podaci/knjižice/video zapisi

Animirani slide show reproduktivnog ciklusa, Queensland Health

Izvori učionice

Ovaj komplet ima magnetsku ploču na kojoj se mogu prikazati muški i ženski reproduktivni sustav (dijelovi prikazani gotovo u prirodnoj veličini). Postoji 30 magnetskih slojeva koji se koriste za demonstraciju menstruacije, ejakulacije, kontracepcije, začeća i trudnoće. Kompleti mogu biti dostupni za iznajmljivanje ili kupnju u regionalnim domovima zdravlja, a mogu se kupiti i u SHQ -u. Reproduktivni kompleti Magno-mate prilično su detaljni i stoga su prikladniji za sedmu godinu i više.


Dostupnost podataka

Sirovi podaci o redoslijedu i broju izraza s klasifikacijom stanica pohranjeni su u bazi podataka ArrayExpress pod pristupnim kodom: E-MTAB-8060. Skupovi podataka mogu se vizualizirati putem web portala www.humanembryo.org.

S obzirom na ranije objavljene skupove podataka koji su ovdje korišteni, jednostanični podaci za sekvence RNA iz Xiang et al. 23 i Zhou i sur. 24 su pohranjene u Gene Expression Omnibus (GEO) pod pristupnim brojevima GSE136447 i GSE109555. Osim toga, podaci o staničnoj liniji iz Takashime i sur. 43 are deposited at Array Express under accession number E-MTAB-2857. Cell line data from Theunissen et al. 75 are deposited at GEO under accession number GSE59435. Cell line data from Rostovskaya et al. 45 are deposited in GEO under accession number GSE 123055.

Immunofluorescence data will be available from the corresponding authors upon reasonable request. Source data are provided with this paper.


Having a baby: Stages of pregnancy by trimester

The stages of pregnancy are separated into three trimesters, with a fourth trimester after birth.

For a pregnant person, feeling a new life developing inside your body is an amazing experience, even though you may not always feel your best during all the stages of pregnancy. One of the biggest changes for most pregnant people is weight gain — a pregnant person carrying one baby should gain between 11 and 40 lbs. (5 to 18 kilograms) by the end of the pregnancy, depending on pre-pregnancy weight, according to the centar za kontrolu i prevenciju bolesti.

But there are many other changes too, and exactly how pregnancy affects the body can be very different from person to person, and even for the same mother from one pregnancy to the next. Some symptoms of pregnancy last for several weeks or months, while other discomforts are temporary or don't affect everyone the same way.

"Pregnancy is a long, 10-month journey," said Dr. Draion Burch, an obstetrician and gynecologist at Magee Womens Hospital at the University of Pittsburgh Medical Center.

A normal pregnancy usually lasts about 40 weeks, counting from the first day of the last menstrual period, which is around two weeks before conception actually occurs. Pregnancy is divided into three trimesters, each lasting between 12 and 13 weeks. During each trimester, changes take place in a pregnant person's body as well as in the developing fetus.

Some medical experts suggest that mothers and doctors should also recognize a "fourth trimester," which is the 12-week period after birth in which babies are adjusting to life outside the womb and women are coping with motherhood and on-going changes in their bodies, according to a paper published in July 2017 in the American Journal of Obstetrics and Gynecology.

Conception & implantation

About two weeks after a period, ovulation occurs, during which the ovaries release typically one egg, but sometimes two or more eggs. The egg or eggs can be fertilized by a sperm cell 12 to 24 hours after release, as the egg travels down the fallopian tube toward the uterus.

The sex of the fetus is determined at the time of fertilization, or conception, and depends on whether the egg receives an X or Y chromosome from a sperm cell. If the egg receives an X chromosome, the baby will be a girl a Y chromosome means the baby will be a boy.

Prema Cleveland Clinic, it takes about three to four days for the fertilized egg (or embryo) to move to the lining of the uterus, where it attaches or implants to the uterine wall. Once the embryo is implanted, the cells start to grow, eventually becoming the fetus and the placenta, which is tissue that attaches to the lining of the uterus. The placenta transports oxygen, nutrients and hormones from the mother's blood to the developing fetus via the umbilical cord throughout pregnancy.

First trimester, weeks 1-12

First trimester changes in the mother:

Pregnant people will experience a lot of symptoms during the first trimester as the body adjusts to the hormonal changes of pregnancy. In the early weeks, the pregnancy may not be showing much on the outside of her body, but inside many changes are taking place.

One of the first changes is the production of human chorionic gonadotropin (hCG) hormone, which shows up in the blood right after conception occurs. Levels of hCG can be detected in a pregnant person's urine about a week after a missed period. Human chorionic gonadotropin is what's detected in a positive home pregnancy test.

Rising levels of hCG and other hormones, such as estrogena, may be responsible for the waves of nausea and vomiting known as morning sickness that's most common during the first few months of pregnancy. Despite its name, morning sickness can occur any time of day.

A pregnant person may also feel more tired than usual during the first trimester, a symptom that's linked with rising levels of the hormone progesterone, which increases sleepiness.

Early in pregnancy, breasts may feel more tender and swollen, another side effect of rising levels of pregnancy hormones. The areolas, the skin around each nipple, will darken and enlarge.

A pregnant person's digestive system may slow down to increase the absorption of beneficial nutrients. But reduced mobility of the digestive system might also trigger such common complaints as heartburn, constipation, bloating and gas, according to the Office on Women's Health (OWH).

Many parts of the body will work harder during pregnancy, including the heart. Heart rate will increase to pump more blood to the uterus, which will supply it to the fetus.

Besides the physical changes, expecting mothers may also experience emotional highs and lows in the early months of her pregnancy and throughout it. These emotions may range from weepiness, mood swings and forgetfulness, to fear, anxiety and excitement.

First trimester embryo development:

A developing baby is called an embryo from the moment conception takes place until the eighth week of pregnancy.

During the first month of pregnancy the heart and lungs begin to develop, and the arms, legs, brain, spinal cord and nerves begin to form, according to the American College of Obstetricians and Gynecologists (ACOG).

The embryo will be about the size of a pea around one month into a pregnancy, Burch said. Around the second month of pregnancy, the embryo has grown to the size of a kidney bean. In addition, the ankles, wrists, fingers and eyelids form, bones appear, and the genitals and inner ear begin to develop.

After the eighth week of pregnancy and until birth occurs, a developing baby is called a fetus.

By the end of the second month, most of the fetus' main organs will have formed, Burch said. At this stage of pregnancy, he stressed, it's extremely important that pregnant women do not take harmful medications, such as illegal drugs. The first trimester is also the period when most miscarriages and birth defects occur. Between 10% and 20% of known pregnancies end in miscarriages, mostly because the fetus is not developing normally, according to the Klinika Mayo. Studies have found the risk of miscarriage drops significantly after the 12th week of pregnancy.

As early as the 10th week of pregnancy, a pregnant person may opt to have a noninvasive prenatal test (NIPT). This testing uses a blood sample from the mother to analyze DNA from the fetus to help determine the risk of the baby being born with certain genetic abnormalities, according to MedlinePlus. The mother can also find out the sex of the baby at this time, also through providing a blood sample that analyzes fetal DNA. None of these tests come in contact with or cause any harm to the fetus.

During the third month of pregnancy, the fetus' bones and muscles begin to grow, buds for future teeth appear, and fingers and toes grow. The intestines begin to form and the skin is almost transparent.

Second trimester, weeks 13-27

Second trimester changes in the mother:

By the second trimester, some of the unpleasant effects of early pregnancy may lessen or disappear as the body adjusts to its changing hormone levels. Sleeping may get easier and energy levels may increase.

Nausea and vomiting usually get better and go away, Burch told Live Science. But other symptoms may crop up as the fetus continues its growth and development.

Pregnant people will start to feel more pelvic pressure, Burch said, adding that the pelvis feels heavy like something is weighing it down.

A more visible baby bump appears as the uterus grows beyond the pelvis, and the skin over the expanding belly may itch as it stretches, according to the OWH.

As the fetus is getting bigger and the mother is gaining more pregnancy weight in the front of her body, she may also experience more back pain, Burch said. A 2020 study published in the Journal of Personalized Medicine found that while most pregnant people experienced back pain, it was worse in those who were not physically active.

Sometime between the 16th and 18th weeks of pregnancy, a first-time mother may feel the first fluttering movements of the fetus, known as quickening, Burch said. It it isn't the first pregnancy, the mother is likely to feel the fetus kicking, squirming or turning even sooner because she knows what to expect, he said.

The 20th week usually marks the halfway point of pregnancy. From about 20 weeks, it is possible to develop preeclampsia, a condition characterized by high-blood pressure, according to the Klinika Mayo. If left untreated, the condition can lead to serious, even fatal, complications for mother and baby. Other symptoms include rapid weight gain and swelling.

Burch encourages his patients to take a "baby-moon" — a mini-vacation or weekend getaway — during the second trimester, and he said the best time to get away is around the 28th week of pregnancy. Expecting mothers are generally feeling pretty good at this point, and there's a lower risk of miscarriage and premature labor. A study published in 2020 in the journal PLOS One, found that for hundreds of thousands of babies, their mother's airplane travel had no adverse effects on the baby's birth weight or gestational age. However, some health professionals and airlines may discourage airplane travel after the 36th week because at that time birth could be just around the corner.

Second trimester fetal development:

In the second trimester, the fetus will be between 3 and 5 inches (7 and 12 centimeters) long, Burch said. Sometime between 18 and 22 weeks, an ultrasound may reveal the sex of the baby, if parents want to know this information in advance.

By the fourth month of pregnancy the fetus' eyebrows, eyelashes, fingernails and the neck form, and the skin has a wrinkled appearance. In addition, during the fourth month the arms and legs can bend, the kidneys start working and can produce urine, and the fetus can swallow and hear, according to the ACOG.

In the fifth month of pregnancy, the fetus is more active and the mother may be able to feel its movements. The fetus also sleeps and wakes on regular cycles. A fine hair (called lanugo) and a waxy coating (called vernix) cover and protect the thin fetal skin.

By the sixth month of pregnancy, hair begins to grow, the eyes begin to open and the brain is rapidly developing. Although the lungs are completely formed, they don't yet function.

Third trimester, weeks 28-40

Third trimester changes in the mother:

During the third trimester, as the mother's enlarged uterus pushes against her diaphragm, a major muscle involved in breathing. Because of this, she may feel short of breath because the lungs have less room to expand, according to Johns Hopkins Medicine. A pregnant person's ankles, hands, feet and face may swell due to fluid retention and slower blood circulation.

A mother-to-be will need to urinate more frequently because of the pressure on her bladder. She may also have more backaches and more pain in the hips and pelvis, as these joints expand in preparation for delivery. Changes in body shape can also make a pregnant person more unstable on their feet and more likely to fall, according to a 2006 study published in the American Journal of Obstetrics and Gynecology.

Her face may develop dark patches of skin, and stretch marks may appear on her belly, thighs, breasts and backside. She may also notice varicose veins on her legs.

In the third trimester, the breasts may start to leak colostrum, a yellow liquid, as they get ready for breastfeeding, according to the OWH. The baby will start to drop lower in the mother's abdomen.

False labor, known as Braxton-Hicks contractions, may begin to occur as the due date gets closer. A "nesting instinct," behavior exhibited in many mammals, may kick in as expecting parents work on baby-proofing their home, shop for baby items, prepare the nursery and await their new arrival.

During the final weeks of pregnancy, it will become harder to find a comfortable sleeping position, adding to the increased levels of fatigue, Burch said.

Third trimester fetal development:

By the seventh month of pregnancy, the fetus kicks and stretches, and can even respond to light and sound, Burch said. Its eyes can also open and close.

During the eighth and ninth months of pregnancy, the fetus gains weight very quickly. Bones harden, but the skull remains soft and flexible so the head can fit through the birth canal. Different regions of the brain are forming, and the fetus is able to hiccup, according to ACOG.

The ninth month is the home stretch of pregnancy, and the fetus is getting ready for birth by turning into a head-down position in the mother's pelvis. The lungs are now fully mature and ready to function on their own.

The definition of a full-term pregnancy is when a baby is born after 39 to 40 weeks (it used to be 37 weeks), Burch said. This is because babies born at full-term had lower risks of problems with breathing, feeding and regulating their temperature than those born earlier, according to the Nacionalni zdravstveni zavodi.

Fourth trimester, post-birth

The period called the "fourth trimester" begins as soon as birth is over. While this can be a joyful and exciting time for most new parents, it can also be extremely challenging and stressful.

In the weeks and months after the baby is born, the mother's body continues to go through major changes as it heals and recovers from pregnancy and birth. At the same time, the mother must grapple with the physical and emotional challenges of feeding and caring for a newborn, Dr. Ilona T. Goldfarb, a maternal health specialist, wrote for the Harvard Health Blog. "Women and their families experience substantial physiological, social and emotional changes," during this time, Goldfarb wrote.

Despite the continuing changes and challenges that occur after childbirth, most mothers visit their obstetrician only once in the weeks after birth. Many health experts agree that this lack of attention to maternal health in the fourth trimester is concerning, especially considering that more than half of pregnancy-related deaths occur after the birth of the child, according to a 2018 report from the ACOG.

Fortunately, several of these experts are putting pressure on the healthcare community to provide more comprehensive postpartum care. Goldfarb recommends pregnant people come up with a postpartum plan to help anticipate difficulties and how to deal with them as they pop up. She also recommends mothers speak with their obstetrician to learn more about the kind of postpartum resources they have.

Additional resources

Pregnancy Day By Day: An Illustrated Daily Countdown to Motherhood, from Conception to ChildbirthView Deal

This article is for informational purposes only, and is not meant to offer medical advice. This article was updated on June 14, 2021 by Live Science contributor Sarah Wild.


Fetal Development: Stages of Growth

The start of pregnancy is actually the first day of your last menstrual period. This is called the gestational age, or menstrual age. It’s about two weeks ahead of when conception actually occurs. Though it may seem strange, the date of the first day of your last period will be an important date when determining your baby’s due date. Your healthcare provider will ask you about this date and will use it to figure out how far along you are in your pregnancy.

How does conception work?

Each month, your body goes through a reproductive cycle that can end in one of two ways. You will either have a menstrual period or become pregnant. This cycle is continuously happening during your reproductive years—from puberty in your teen years to menopause around age 50.

In a cycle that ends with pregnancy, there are several steps. First, a group of eggs (called oocytes) gets ready to leave the ovary for ovulation (release of the egg). The eggs develop in small, fluid-filled cysts called follicles. Think of these follicles as small containers for each immature egg. Out of this group of eggs, one will become mature and continue on through the cycle. This follicle then suppresses all the other follicles in the group. The other follicles stop growing at this point.

The mature follicle now opens and releases the egg from the ovary. This is ovulation. Ovulation generally happens about two weeks before your next menstrual period begins. It’s generally in the middle of your cycle.

After ovulation, the opened (ruptured) follicle develops into a structure called the corpus luteum. This secretes (releases) the hormones progesterone and estrogen. The progesterone helps prepare the endometrium (lining of the uterus). This lining, is the place where a fertilized egg settles to develop. If you don’t become pregnant during a cycle, this lining is what is shed during your period.

On average, fertilization happens about two weeks after your last menstrual period. When the sperm penetrates the egg, changes occur in the protein coating of the egg to prevent other sperm from entering.

At the moment of fertilization, your baby’s genetic make-up is complete, including its sex. The gender of your baby depends on what sperm fertilizes the egg at the moment of conception. Generally, women have a genetic combination of XX and men have XY. As the mother, you provide each egg with an X. Each sperm can be either an X or a Y. If the fertilized egg and sperm is a combination of an X and Y, it’s a boy. If there are two Xs, it’s a girl.

What happens right after conception?

Within 24 hours after fertilization, the egg begins rapidly dividing into many cells. It remains in the fallopian tube for about three days after conception. Then the fertilized egg (now called a blastocyte) continues to divide as it passes slowly through the fallopian tube to the uterus. Once there, its next job is to attach to the endometrium. This is called implantation.

Before implantation though, the blastocyte breaks out of its protective covering. When the blastocyte makes contact with the endometrium, the two exchange hormones to help the blastocyte attach. Some women notice spotting (slight bleeding) during the one or two days when implantation happens. This is normal and isn’t something you should worry about. At this point, the endometrium becomes thicker and the cervix (the opening between your uterus and birth canal) is sealed by a plug of mucus.

Within three weeks, the blastocyte cells ultimately form a little ball, or an embryo. By this time, the baby’s first nerve cells have formed.

Your developing baby has already gone through a few name changes in the first few weeks of pregnancy. Generally, your baby will be called an embryo from conception until the eighth week of development. After the eighth week, the baby will be called a fetus until it’s born.

How early can I know I’m pregnant?

From the moment of conception, the hormone human chorionic gonadotrophin (hCG) will be present in your blood. This hormone is created by the cells that form the placenta (food source for your baby in the womb). It’s also the hormone detected in a pregnancy test. Even though this hormone is there from the beginning, it takes time for it to build within your body. It typically takes three to four weeks from the first day of your last period for the hCG to increase enough to be detected by pregnancy tests.

When should I reach out to my healthcare provider about a new pregnancy?

Most healthcare providers will have you wait to come in for an appointment until you have had a positive home pregnancy test. These tests are very accurate once you have enough hCG circulating throughout your body. This can be a few weeks after conception. It’s best to call your healthcare provider once you have a positive pregnancy test to schedule your first appointment.

When you call, your healthcare provider may ask you if you are taking a prenatal vitamin. These supplements contain something called folic acid. It’s important that you get at least 400mcg of folic acid each day during a pregnancy to make sure your baby’s neural tube (beginning of the baby’s brain and spine) develops correctly. Many healthcare providers suggest that you take prenatal vitamins with folic acid even when you aren’t pregnant. If you weren’t taking prenatal vitamins before your pregnancy, your provider may ask you to start as early as possible.

What’s the timeline for my baby’s development?

Your baby will change a lot throughout a typical pregnancy. This time is divided into three stages, called trimesters. Each trimester is a set of about three months. Your healthcare provider will probably talk to you about your baby’s development in terms of weeks. So, if you are three months pregnancy, you are about 12 weeks.

You will see distinct changes in your baby, and yourself, during each trimester.

Traditionally, we think of a pregnancy as a nine-month process. However, this isn’t always the case. A full-term pregnancy is 40 weeks, or 280 days. Depending on what months you are pregnant during (some are shorter and some longer) and what week you deliver, you could be pregnant for either nine months or 10 months. This is completely normal and healthy.

Once you get close to the end of your pregnancy, there are several category names you might hear regarding when you go into labor. These labels divide up the last few weeks of pregnancy. They’re also used to look out for certain complications in newborns. Babies that are born in the early term period or before may have a higher risk of breathing, hearing or learning issues than babies born a few weeks later in the full term time frame. When you’re looking at these labels, it’s important to know how they’re written. You may see the week first (38) and then you’ll see two numbers separated by a slash mark (6/7). This stands for how many days you currently are in the gestational week. So, if you see 38 6/7, it means that you are on day 6 of your 38th week.

The last few weeks of pregnancy are divided into the following groups:

  • Early term: 37 0/7 weeks through 38 6/7 weeks.
  • Full term: 39 0/7 weeks through 40 6/7 weeks.
  • Late term: 41 0/7 weeks through 41 6/7 weeks.
  • Post term: 42 0/7 weeks and on.

Talk to your healthcare provider about any questions you may have about your baby’s gestational age and due date.

Stages of Growth Month-by-Month in Pregnancy

First trimester

The first trimester will span from conception to 12 weeks. This is generally the first three months of pregnancy. During this trimester, your baby will change from a small grouping of cells to a fetus that is starting to have a baby’s features.

Month 1 (weeks 1 through 4)

As the fertilized egg grows, a water-tight sac forms around it, gradually filling with fluid. This is called the amniotic sac, and it helps cushion the growing embryo.

During this time, the placenta also develops. The placenta is a round, flat organ that transfers nutrients from the mother to the baby, and transfers wastes from the baby. Think of the placenta as a food source for your baby throughout the pregnancy.

In these first few weeks, a primitive face will take form with large dark circles for eyes. The mouth, lower jaw and throat are developing. Blood cells are taking shape, and circulation will begin. The tiny "heart" tube will beat 65 times a minute by the end of the fourth week.

By the end of the first month, your baby is about 1/4 inch long – smaller than a grain of rice.

Month 2 (weeks 5 through 8)

Your baby's facial features continue to develop. Each ear begins as a little fold of skin at the side of the head. Tiny buds that eventually grow into arms and legs are forming. Fingers, toes and eyes are also forming.

The neural tube (brain, spinal cord and other neural tissue of the central nervous system) is well formed now. The digestive tract and sensory organs begin to develop too. Bone starts to replace cartilage.

Your baby’s head is large in proportion to the rest of its body at this point. At about 6 weeks, your baby's heart beat can usually be detected.

After the 8th week, your baby is called a fetus instead of an embryo.

By the end of the second month, your baby is about 1 inch long and weighs about 1/30 of an ounce.

Month 3 (weeks 9 through 12)

Your baby's arms, hands, fingers, feet and toes are fully formed. At this stage, your baby is starting to explore a bit by doing things like opening and closing its fists and mouth. Fingernails and toenails are beginning to develop and the external ears are formed. The beginnings of teeth are forming under the gums. Your baby's reproductive organs also develop, but the baby's gender is difficult to distinguish on ultrasound.

By the end of the third month, your baby is fully formed. All the organs and limbs (extremities) are present and will continue to develop in order to become functional. The baby’s circulatory and urinary systems are also working and the liver produces bile.

At the end of the third month, your baby is about 4 inches long and weighs about 1 ounce.

Since your baby's most critical development has taken place, your chance of miscarriage drops considerably after three months.

Second trimester

This middle section of pregnancy is often thought of as the best part of the experience. By this time, any morning sickness is probably gone and the discomfort of early pregnancy has faded. The baby will start to develop facial features during this month. You may also start to feel movement as your baby flips and turns in the uterus. During this trimester, many people find out the sex of the baby. This is typically done during an anatomy scan (an ultrasound that checks your baby’s physical development) around 20 weeks.

Month 4 (weeks 13 through 16)

Your baby's heartbeat may now be audible through an instrument called a doppler. The fingers and toes are well-defined. Eyelids, eyebrows, eyelashes, nails and hair are formed. Teeth and bones become denser. Your baby can even suck his or her thumb, yawn, stretch and make faces.

The nervous system is starting to function. The reproductive organs and genitalia are now fully developed, and your doctor can see on ultrasound if you are having a boy or a girl.

By the end of the fourth month, your baby is about 6 inches long and weighs about 4 ounces.

Month 5 (weeks 17 through 20)

At this stage, you may begin to feel your baby moving around. Your baby is developing muscles and exercising them. This first movement is called quickening and can feel like a flutter.

Hair begins to grow on baby's head. Your baby's shoulders, back and temples are covered by a soft fine hair called lanugo. This hair protects your baby and is usually shed at the end of the baby's first week of life.

The baby's skin is covered with a whitish coating called vernix caseosa. This "cheesy" substance is thought to protect your baby's skin from the long exposure to the amniotic fluid. This coating is shed just before birth.

By the end of the fifth month, your baby is about 10 inches long and weighs from 1/2 to 1 pound.

Month 6 (weeks 21 through 24)

If you could look inside the uterus at your baby right now, you would see that your baby's skin is reddish in color, wrinkled and veins are visible through the baby's translucent skin. Baby's finger and toe prints are visible. In this stage, the eyelids begin to part and the eyes open.

Baby responds to sounds by moving or increasing the pulse. You may notice jerking motions if baby hiccups.

If born prematurely, your baby may survive after the 23rd week with intensive care.

By the end of the sixth month, your baby is about 12 inches long and weighs about 2 pounds.

Month 7 (weeks 25 through 28)

Your baby will continue to mature and develop reserves of body fat. At this point, the baby's hearing is fully developed. The baby changes position frequently and responds to stimuli, including sound, pain and light. The amniotic fluid begins to diminish.

If born prematurely, your baby would be likely to survive after the seventh month.

At the end of the seventh month, your baby is about 14 inches long and weighs from 2 to 4 pounds.

Third trimester

This is the final part of your pregnancy. You may be tempted to start the countdown till your due date and hope that it would come early, but each week of this final stage of development helps your baby prepare for childbirth. Throughout the third trimester, your baby will gain weight quickly, adding body fat that will help after birth.

Remember, even though popular culture only mentions nine months of pregnancy, you may actually be pregnant for 10 months. The typical, full-term pregnancy is 40 weeks, which can take you into a tenth month. It’s also possible that you can go past your due date by a week or two (41 or 42 weeks). Your healthcare provider will monitor you closely as you approach your due date. If you pass your due date, and don’t go into spontaneous labor, your provider may induce you. This means that medications will be used to make you go into labor and have the baby. Make sure to talk to your healthcare provider during this trimester about your birth plan.

Month 8 (weeks 29 through 32)

Your baby will continue to mature and develop reserves of body fat. You may notice that your baby is kicking more. Baby's brain is developing rapidly at this time, and your baby can see and hear. Most internal systems are well developed, but the lungs may still be immature.

Your baby is about 18 inches long and weighs as much as 5 pounds.

Month 9 (weeks 33 through 36)

During this stage, your baby will continue to grow and mature. The lungs are close to being fully developed at this point.

Your baby's reflexes are coordinated so he or she can blink, close the eyes, turn the head, grasp firmly, and respond to sounds, light, and touch.

Your baby is about 17 to 19 inches long and weighs from 5 ½ pounds to 6 ½ pounds.

Month 10 (Weeks 37 through 40)

In this final month, you could go into labor at any time. You may notice that your baby moves less due to tight space. At this point, your baby’s position may have changed to prepare for birth. Ideally, the baby is head down in in your uterus. You may feel very uncomfortable in this final stretch of time as the baby drops down into your pelvis and prepares for birth.

Your baby is ready to meet the world at this point.

Your baby is about 18 to 20 inches long and weighs about 7 pounds.

Last reviewed by a Cleveland Clinic medical professional on 04/16/2020.

Reference

  • The American College of Obstetricians and Gynecologists. How your fetus grows during pregnancy. Accessed 4/17/2020.
  • American Pregnancy Association. Fetal Development. Accessed 4/17/2020.
  • Centar za kontrolu i prevenciju bolesti. During Pregnancy. Accessed 4/17/2020.
  • US Department of Health and Human Services, Office on Women’s Health. Stages of pregnancy. Accessed 4/17/2020.

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Cleveland Clinic je neprofitni akademski medicinski centar. Oglašavanje na našim stranicama podržava našu misiju. Ne podržavamo proizvode ili usluge klinike koja nije Cleveland. Policy

Cleveland Clinic je neprofitni akademski medicinski centar. Oglašavanje na našim stranicama podržava našu misiju. Ne podržavamo proizvode ili usluge klinike koja nije Cleveland. Policy

Cleveland Clinic je neprofitni akademski medicinski centar. Oglašavanje na našim stranicama podržava našu misiju. Ne podržavamo proizvode ili usluge klinike koja nije Cleveland. Policy

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8. Conclusions

CD147 is a highly glycosylated cell surface type I transmembrane protein [1,3] involved in a range of process, including angiogenesis [114,151], inflammatory diseases and cancer progression. Multiple human pathogens utilize CD147 for efficient infection. CD147 also acts as a hypoxia-responsive molecule. In addition, remarkable heterogeneity in CD147 expression between different tumor types has been observed. For example, the positivity rate of CD147 was 67.76% in epithelium-derived carcinomas, including lung cancer, hepatocellular carcinoma and breast cancer, whereas this rate was only 5.18% in normal epithelial tissues [181]. CD147 promotes tumor invasion and metastasis by stimulating MMP synthesis in neighboring fibroblasts [66] and induces chemoresistance in tumor cells by stimulating them to produce hyaluronan [147]. Indeed, the inhibition of CD147 gene expression via RNA interference reduces tumor cell invasion and tumorigenicity and increases chemosensitivity to paclitaxel [182]. In several cancers, CD147 expression is so elevated that it is now used as a prognostic biomarker to diagnose early-stage disease and an effective therapeutic target for some cancers. Indeed, exciting clinical progress has been made in HCC treatment using CD147-directed monoclonal antibodies. Although CD147 has been extensively investigated, some questions and uncertainties remain. Whether CD147-Abs cause side effects in the human body requires investigation. Therefore, CD147’s suitability as a potential therapeutic target should be assessed. It is thought that a greater understanding of the physiological and pathological mechanisms of CD147 and other molecular factors involved in disease prognosis will lead to new insights into accurate prognostic prediction, which is critical to the selection of appropriate therapeutic approaches. Moreover, the prognostic role of CD147 could be used to further analyze the overall survival of patients with carcinomas such as glioma and HCC [57,73]. Another potential utility of targeting CD147 is to reduce VEGF secretion and EC migration in the KS microenvironment [114].

Meanwhile, although transmembrane CD147 has been proposed to act as a receptor for several extracellular proteins, such as the cyclophilin class of enzymes [3], CD147 also exhibits ligand activity. This ligand activity leads to the CD147-mediated stimulation of multiple protein families and is thought to underlie the progression of many diseases, such as RA [50], and most cancers, including retinoblastoma [99]. Agents targeting either CD147 or cyclophilin activity show significant anti-inflammatory effects in experimental models, suggesting that CD147-cyclophilin interactions represent dual targets for new anti-inflammatory therapeutics [183], especially for the natural soluble forms present in ocular and synovial fluids. Similar approaches are currently under investigation to develop reagents to inhibit selective functions of CD147, such as the targeting of specific domains of the molecule. Progress in these endeavors will likely provide new treatment opportunities for several inflammatory diseases, including RA, psoriasis and asthma, and may also contribute to the treatment of such diseases as atherosclerosis and cancer. Therefore, novel methods or ideas should be proposed to study CD147, such as the use of double-specific antibodies, which may represent a new direction for treatment.