两个胎盘分开两个胎盘融合两层绒毛膜两层绒毛膜已融合两层羊膜两层羊膜
Clinical CharacteristicsMultiplegestationshouldbesuspectedifuterine size is greaterthan expectedforgestational age, multiple fetalheart ratesare heard, multiple fetal parts are felt, thehCGandmaternalserumalpha-fetoproteinlevelsare elevatedforgestational age. Diagnosis is confirmed bysonogram
Clinical Characteristics. ◼ Multiple gestation should be suspected if uterine size is greater than expected for gestational age, multiple fetal heart rates are heard, multiple fetal parts are felt, the hCG and maternal serum alphafetoprotein levels are elevated for gestational age. Diagnosis is confirmed by sonogram
Zygosity双生子卵性，Placentation，and MortalityDichorionic/Diamnioticand DizygoticTwins (>70% of all twins). Twins are aproduct of fertilization of multiple ovaEachfetushasitsownplacenta,andeachfetusis containedwithin a completeamniotic-chorionicmembrane
Zygosity 双生子卵性, Placentation, and Mortality ◼ Dichorionic/Diamniotic and Dizygotic Twins (>70% of all twins). Twins are a product of fertilization of multiple ova. Each fetus has its own placenta, and each fetus is contained within a complete amniotic-chorionic membrane
MonozygoticTwinsMonozygoticTwins同卵双生(<30%ofallpregnancies).Thesetwinsaremultiplegestations resultingfromcleavageof a single, fertilized ovum. The timing ofcleavagedeterminesthe placentation ofthepregnancy
Monozygotic Twins ◼ Monozygotic Twins 同卵双生 ◼ (<30% of all pregnancies). These twins are multiple gestations resulting from cleavage of a single, fertilized ovum. The timing of cleavage determines the placentation of the pregnancy