Prenatal Diagnosis of Zygosity by Fetal DNA Analysis, a Contribution to the Management of Multiple Pregnancies

Abstract

Objective: To evaluate the contribution of prenatal diagnosis of zygosity by fetal DNA analysis to the management of multiple pregnancies. Methods: Between March 1999 and March 2000, 31 same-sex multiple pregnancies, were referred to our Institute during their second trimester to have amniocentesis done. Fetal DNA variants were studied in addition to karyotype. The main indications for amniocentesis were fetal growth discordance, fetal malformations or selective pregnancy termination. Zygosity results were compared to the first-trimester ultrasound diagnosis. Results: 21 out of the 31 multiple pregnancies were dizygous, and 10 out of the 31 pregnancies were monozygous. First-trimester ultrasound provided information on chorionicity only in 24 out of the 31 cases (77%). Of these 24 reports, 21 proved to be correct (87.5%). Moreover, in 2 cases among 14 pregnancies with growth discordance, DNA analysis ruled out a twin-to-twin transfusion syndrome, while ultrasound could not yield a conclusion. In 2 twin pregnancies with fetal malformations affecting one of the fetuses, DNA analysis made it possible to assess the risk for the other twin. In the 5 cases leading to selective termination, prenatal diagnosis of zygosity had a decisive value for the surviving fetus. Conclusion: Fetal DNA analysis is a simple and highly useful test for prenatal diagnosis of zygosity in the management of complicated multiple pregnancies.

The Frequency and Clinical Significance of Twin Gestations According to Zygosity and Chorionicity

“…In addition, zygosity is of medical importance in organ transplantation between twins and the need for immunosuppressive agents and in matters of inheritance of cancer or other specific diseases (Bamforth & Machin, 2004;Hur, 2009;Kessaris et al, 2008;Rosenberg et al, 2009;St Clair et al, 1998). Prenatally, determining accurate zygosity is of great significance in fetal reduction when chorionicity remains little convincing despite scrutinizing ultrasound examinations because of fetal crowding, decreased amniotic fluid and maternal obesity (Levy et al, 2002;Peng et al, 2007;Stagiannis et al, 1995;Vayssiere et al, 1996). Furthermore, in twin studies, zygosity plays a key role in determining the relative contribution of genetics and the environment to the human condition and behavior for life (Clausson et al, 2000;Grjibovski et al, 2005;Liu et al, 2004;Tanner et al, 1999).…”

Diagnostic échographique de chorionicité dans les grossesses multiples

“…La sensibilité et la spécificité sont excellentes pour les études qui se sont intéressées de façon prospective à ce [11]. La visualisation de deux masses placentaires distinctes est un très bon argument de bichorialité, mais en pratique rarement observé de façon formelle à ces termes [10]. De mauvaises interprétations, dans les deux sens, sont possibles avec ce seul critère.…”

“…À l'occasion d'un travail concernant le diagnostic prénatal de la zygotie [10], nous avons suivi, entre mars 1999 et mars 2000, les grossesses multiples qui bénéficiaient d'une amniocentèse à l'institut de puériculture et de périnatologie pour détermination du caryotype et pour lesquelles les sexes foetaux étaient identiques. Nous avons ainsi étudié 31 dossiers consécutifs de grossesses multiples.…”

Comparing Facial 3D Analysis With DNA Testing to Determine Zygosities of Twins

“…Not only genes, but also epigenetic and environmental factors –– frequently called ‘functional matrix’ or ‘nurture’ –– have an influence on faces in the course of growth (Corruccini, 1999; Galton, 1875; Kempthorne & Osborne, 1961; Lundström, 1954). Modern DNA analyses are routine today and allow high-quality precision in zygosity determination even before birth (Levy et al, 2002). Postnatally, these tests are easier to do, but they can also be quite expensive if used for heritability determinations in a large group of twins (Becker et al, 1997; Forget-Dubois et al, 2003).…”