Determining zygosity in early pregnancy by ultrasound

Abstract

OBJECTIVES: First-trimester ultrasound can reliably determine chorionicity but not zygosity. We set out to investigate whether it may be possible to determine zygosity using ultrasound by noting the number of corpora lutea (CLs), structures which reflect ovulation. In the presence of a dichorionic twin pregnancy, the identification of one CL would suggest that twins are monozygotic whereas two CLs implies dizygosity. METHODS: This was a retrospective analysis of predominantly spontaneous twin pregnancies presenting for an early pregnancy ultrasound at 5-8-completed weeks of gestation. Placentation was correlated with presumed zygosity as predicted by the number of CLs present. RESULTS: Of 33..