title: Statistical approach to prenatal zygosity assessment following a decade of molecular aneuploidy screening.
abstract: In twin pregnancy studies, molecular genetic techniques have rarely been used to determine zygosity, despite their known precision and accuracy. The present work aimed to assess the power of discrimination in zygosity assessment, using a set of microsatellite markers that were routinely used for aneuploidy screening by multiplex-PCR in a prenatal context. Rapid aneuploidy screening using a group of 20 microsatellite markers (STRs) located on chromosomes 13, 18, 21 and X has been performed in our lab for over 10 years, with a total of approximately 1,500 samples studied to date. A retrospective analysis of the 257 prenatal samples from multiple pregnancies was carried out. A subset of 14 cases presenting theoretical monozygosity were re-evaluated by the use of biostatistics tools accessed via the ZygProb website. Further monozygosity determination relative to dizygosity was calculated, given an estimated overall error value of 0.093%. The results show that monozygosity had been correctly determined in all our previously studied twins. This work demonstrates that accurate zygosity assessment can be achieved with the same STRs applied in aneuploidy screening with a high power of discrimination and a matching probability of over 99.999999%.
authors.affiliation: Centre for Medical Genetics Doutor Jacinto Magalhães, National Health Institute Doutor Ricardo Jorge, Porto, Portugal.
authors.forename: Sílvia
authors.initials: S
authors.lastname: Pires
authors.forename: António J A
authors.initials: AJ
authors.lastname: Nogueira
authors.forename: Odília
authors.initials: O
authors.lastname: Pinho
authors.forename: Tiago
authors.initials: T
authors.lastname: Delgado
authors.forename: Mário
authors.initials: M
authors.lastname: Sousa
authors.forename: Rosário
authors.initials: R
authors.lastname: Santos
authors.forename: Paula
authors.initials: P
authors.lastname: Jorge
mesh_terms: D000782:Aneuploidy; D005260:Female; D006801:Humans; D018895:Microsatellite Repeats; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000235:genetics*; D011295:Prenatal Care; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic