Two Corpora Lutea Seen at 6–13 Weeks' Gestation Infers Dizygosity Among Spontaneous Same-Sexed Dichorionic Twins

Abstract

Current ultrasound techniques can accurately determine the chorionicity of twins, but not zygosity. We previously proposed that the zygosity of spontaneously conceived twins can be determined at early ultrasound, where 2 corpora lutea infers dizygosity, and 1 implies monozygosity. Here we did a case series, comparing zygosity predicted using this method with definitive DNA genotyping of twins after birth. We retrospectively identified 14 ultrasound reports of spontaneous twin pregnancies at 6(+0 days) to 13+6 weeks' gestation, where both ovaries were seen and the number of corpora lutea documented. We visited all twin pairs, obtained buccal smears, and determined zygosity by genotyping 9 independent microsatellite markers. All 8 cases where 2 corpora lutea were seen were dizygotic pregnancies. One further case where 3 corpora lutea were seen was also dizygotic. All 3 sets of monozygotic twins had 1 corpus luteum. There were 2 cases incorrectly assigned, where 1 corpus luteum was seen in dizygotic pregnancies. We conclude if 2 corpora lutea are seen at a first trimester ultrasound of spontaneously conceived dichorionic twins, they appear to be almost certainly dizygotic. However, if 1 corpus luteum is seen in dichorionic twins, zygosity cannot be determined with certainty since it is either monozygotic, or dizygotic where a second corpus luteum has been missed.

The mystery of monozygotic twinning II: What can monozygotic twinning tell us about Amyoplasia from a review of the various mechanisms and types of monozygotic twinning?

“…It is known that 50%–70% of all human conceptions are miscarried or aborted (Landy & Keith, 1998; Macklon et al, 2002; van den Berg et al, 2012). It is also known that once twins can be identified by ultrasound in humans by observing multiple gestational sacs and by multiple corpora lutea in the case of dizygotic (DZ) twins (Woo et al, 2009), as many as 80% of twin pregnancies convert to singletons or are lost (Jauniaux et al, 1988; Levi, 1976). This loss seems likely to particularly occur in MZ twins related both to severe developmental anomalies (Pharoah et al, 2009) and to early demise secondary to untreated twin–twin transfusion syndrome (TTTS) (Glinianaia et al, 2011) and other vascular compromise.…”

A genome wide linkage scan for dizygotic twinning in 525 families of mothers of dizygotic twins

“…Women with a history of DZ twinning have an increased incidence of multiple follicle growth (Martin et al, 1991;Gilfillan et al, 1996) and increased DZ twinning in older women is thought to result from depletion of the ovarian follicle pool and a subsequent rise in concentrations of follicle-stimulating hormone (FSH) (Lambalk et al, 1998). There is little direct evidence for increased twin ovulations in women leading to DZ twins, but in a small series of women all eight cases where two corpora lutea were seen at the first trimester ultrasound were DZ twin pregnancies (Woo et al, 2009).…”