Twin Pregnancy at 12 Weeks - PDF

**A twin pregnancy is identified at 12 weeks\' gestation on antenatal ultrasound. One placenta and one separate amniotic sac are identified. In which ONE of the following scenarios is this is MOST LIKELY to arise?** Monozygotic (Identical) twins: \[Figure 133\] They develop from a single fertilize...

**A twin pregnancy is identified at 12 weeks\' gestation on antenatal ultrasound. One placenta and one separate amniotic sac are identified. In which ONE of the following scenarios is this is MOST LIKELY to arise?** Monozygotic (Identical) twins: \[Figure 133\] They develop from a single fertilized ovum but the resulting zygote splits into two. This splitting may be at various stages of the early development of the zygote: Very early separation of the morula Separation of the inner cell mass of an early blastocyst Separation of the bilaminar germ disc of a late blastocyst Since the monozygotic twins arise from one ovum and one sperm, they are of the same sex and they are identical in their external features.