Two consecutive singleton pregnancies versus one twins pregnancy as preferred outcome of in vitro fertilization for mothers and infants: a retrospective case-control study.

Objective: Many infertile couples request a multiple embryo transfer because they desire more than one child. Based on this consideration, the current study aimed to compare the reproductive and perinatal outcomes of two consecutive singleton pregnancies versus one twin pregnancy in a large cohort of in vitro fertilization (IVF) patients.

Research Design And Methods: Retrospective analysis of data from patients with clinical twin pregnancy after IVF fresh cycles and from patients with two consecutive IVF fresh cycles and clinical singleton pregnancy.

Main Outcome Measures: Miscarriage rate, delivery rate, gestational age at birth, neonatal birth weight, and perinatal complications. A sub-analysis of data according to vanishing twin syndrome (VTS) was also performed.

Results: A total of 18,703 autologous fresh cycles were analyzed. One hundred seven patients had two consecutive singleton clinical pregnancies, whereas one clinical twin pregnancy occurred in 641 women. In patients who had two consecutive singleton clinical pregnancies the rates of overall pregnancies lost (odds ratio [OR] 4.9, 95% confidence interval [CI] 3.4, 6.9) and live births (OR 0.2, 95% CI 0.1, 0.3) were, respectively, higher and lower when compared to patients who had one clinical twin pregnancy. That data did not change after sub-analysis for VTS. The overall risk of perinatal complications was significantly higher in patients who had one twin delivery rather than patients who had two consecutive singleton deliveries (OR 31.8, 95% CI 14.1, 71.5). No difference between groups was detected in terms of intrauterine/neonatal deaths, perinatal mortality and neonatal intensive care unit admission. Data did not change after adjusting for confounders.

Conclusions: When compared with two consecutive singleton pregnancies, twin pregnancies are characterized by higher success rates but worse perinatal outcomes irrespectively of VTS. Well designed prospective controlled studies are needed to confirm or rebut current retrospective findings.