Monozygotic twinning after assisted reproductive techniques: a phenomenon independent of micromanipulation

A 3 year retrospective analysis was conducted of pregnancies achieved after various assisted reproductive treatment modalities in our infertility prac tice, to calculate and compare the rates of monozygotic twinning (MZT), A t otal of 731 pregnancies achieved after various assisted reproduction treatm ents were reviewed. Gonadotrophin therapy for induction of ovulation and co ntrolled ovarian hyperstimulation (COH) yielded 129 clinical pregnancies. C onventional IVF yielded 139 pregnancies. IVF and intracytoplasmic sperm inj ection (ICSI) with or without assisted hatching (AH) yielded 463 pregnancie s, all during the same time period. The rates of multiple pregnancy (monozy gotic and dizygotic) twins and triplets were recorded. MZT was found in 1.5 % of ovulation induction or COH pregnancies (2/129), The incidence of MZT a fter conventional IVF was 0.72% (1/139), After IVF-ICSI/AH, MZT was found i n 0.86% (4/463), The overall rate of MZT was 0.95% (7/731), Five cases were dizygotic triplets and two cases were monozygotic twins. We found the rate of MZT after assisted reproduction treatment increased more than two-fold over the background rate in the general population. Dizygotic triplets were found more often than monozygotic twins. The rate of MZT was consistently increased, irrespective of treatment modality or micromanipulation, This ma y signify that the aetiology of increased MZT after assisted reproduction i s the gonadotrophin treatment rather than in-vitro conditions, micromanipul ation, or multiple embryo transfer.