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

Published online by Cambridge University Press:  21 February 2012

Jean Woo ,
Stephen Tong ,
Megan J. Campbell ,
Leanne Wallace ,
Simon Meagher ,
Grant W. Montgomery ,
Fay Chao ,
Weng Chan  and
Beverley Vollenhoven
Jean Woo
Affiliation:
Southern Health, Women's and Children's Program, Victoria, Australia.
Stephen Tong*
Affiliation:
Southern Health, Women's and Children's Program, Victoria, Australia; Department of Obstetrics and Gynaecology, Monash University, Victoria, Australia; Monash Ultrasound for Women, Monash IVF, Epworth Hospital, Richmond, Victoria, Australia. Stephen.Tong@med.monash.edu.au
Megan J. Campbell
Affiliation:
Molecular Epidemiology Group, Queensland Institute of Medical Research, Brisbane, Australia.
Leanne Wallace
Affiliation:
Molecular Epidemiology Group, Queensland Institute of Medical Research, Brisbane, Australia.
Simon Meagher
Affiliation:
Monash Ultrasound for Women, Monash IVF, Epworth Hospital, Richmond, Victoria, Australia.
Grant W. Montgomery
Affiliation:
Molecular Epidemiology Group, Queensland Institute of Medical Research, Brisbane, Australia.
Fay Chao
Affiliation:
Southern Health, Women's and Children's Program, Victoria, Australia.
Weng Chan
Affiliation:
Southern Health, Women's and Children's Program, Victoria, Australia.
Beverley Vollenhoven
Affiliation:
Southern Health, Women's and Children's Program, Victoria, Australia; Department of Obstetrics and Gynaecology, Monash University, Victoria, Australia.
*
*Address for correspondence: Dr Stephen Tong, Department of Obstetrics and Gynaecology, Monash Medical Centre, 246 Clayton Rd., Clayton 3168, Victoria, Australia.

Abstract

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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.

Keywords

Zygosityultrasoundchorionicitytwinscorpus luteum
Type
Articles
Information
Twin Research and Human Genetics , Volume 12 , Issue 2: SPECIAL SECTION: Genes for Health Meeting 2009 , 01 April 2009 , pp. 180 - 182
Copyright
Copyright © Cambridge University Press 2009