Ku France, tsiku loyembekezeredwa la kubereka limayembekezeredwa mwadongosolo pakadutsa miyezi isanu ndi inayi kuchokera tsiku loyembekezeredwa la kuyambika kwa mimba, mwachitsanzo, masabata 41 (masabata a amenorrhea, mwachitsanzo, masabata opanda kusamba) (1). Mwachitsanzo, ngati tsiku la nthawi yotsiriza ndi March 10, chiyambi cha mimba chikuyerekezedwa, pazochitika za ovulatory nthawi zonse, March 24; DPA idakhazikitsidwa pa Disembala 24 (Marichi 24 + miyezi 9). Kuti awerenge izi, gynecologist kapena mzamba amagwiritsa ntchito "dimba la mimba".

Komabe, ili ndi tsiku longoyerekeza lomwe zinthu zosiyanasiyana zingakhudze:

• nthawi yozungulira: njira yowerengera iyi ndi yovomerezeka pamizere yokhazikika ya masiku 28
• tsiku la ovulation lomwe limatha kusiyanasiyana, ngakhale pafupipafupi, kapenanso kuchokera ku mkombero wina kupita ku wina
• nthawi yopulumuka ya dzira ndi umuna, zomwe zingakhudze tsiku la umuna

Chida china chidzakuthandizani kutsimikizira kapena kukonza tsiku loyamba lachidziwitso ichi: mimba yoyamba ya ultrasound yomwe inachitika pa 12 WA ndipo imatchedwanso "chibwenzi cha ultrasound". Panthawi ya ultrasound, dokotala adzawerengera chiwerengero cha ana omwe ali ndi mimba, ayang'ane mphamvu zake ndikuchita biometry (kutenga miyeso) zomwe zidzatheke kuwerengera zaka za mimba choncho tsiku loyembekezeredwa lobadwa. Adzayezedwa:

• kutalika kwa cranio-caudal kapena LCC, yomwe imafanana ndi kutalika kwa mutu mpaka matako a mluza.
• Biparietal awiri kapena Bip, kutanthauza m'mimba mwake wa chigaza

Mfundo ziwirizi zimafaniziridwa ndi zokhotakhota ndikuloleza chibwenzi chapakati komanso kuyerekezera zaka za mwana wosabadwayo mpaka mkati mwa masiku atatu. Ultrasound iyi imatengedwa kuti ndiyo njira yabwino kwambiri yopangira chibwenzi (3).

Ngakhale ultrasound ingakhale yodalirika zaka za mimba, palinso deta ina yomwe ingakhudze tsiku lobadwa: nthawi ya mimba yokha. Komabe, uku ndi kuyerekezera; Komanso, m'mayiko ambiri, nthawi ya mimba si masamu pa miyezi 9 koma sabata m'mbuyomo, mwachitsanzo 40 milungu. (3) Malingana ndi njira zowerengera, chibadwa ndi makhalidwe ena a amayi, nthawi ya mimba imasiyana pakati pa masiku 280 ndi 290 kuyambira tsiku loyamba la nthawi yotsiriza (kwa nthawi zonse kwa masiku 28). Kutalika kwa mimba kotero kumasiyana pakati pa 40 + 0 ndi 41 + masabata atatu (3). Kafukufuku waposachedwa (4) adawonetsanso kuti nthawi yayitali kuyambira nthawi ya ovulation mpaka kubereka inali masiku 5 (ie masabata 268 ndi masiku 38) okhala ndi kusiyana kwakukulu (mpaka masabata asanu) kutengera mayi.