Perinatal outcome of pregnancies after assisted reproduction: a case-control study.

OBJECTIVE: We conducted a case-control study of all pregnancies obtained with assisted reproduction technology in the Dutch-speaking part of Belgium from 1992 until 1997 to investigate differences in peripartum obstetric events and the perinatal outcome. STUDY DESIGN: Three thousand fifty-seven singleton and 1241 twin pregnancies were studied. About 90% of pregnancies resulted from in vitro fertilization; the remainder resulted from intracytoplasmic sperm injection. Control subjects were selected from a regional register and were matched for maternal age, parity, fetal sex, plurality, and date of delivery. The main outcome measures were duration of gestation, birth weight, perinatal death, perinatal morbidity, incidence of congenital malformations, and incidence of cesarean delivery. RESULTS: Odds ratios and 95% confidence intervals were 2.6 (1.4-4.8) for perinatal mortality, 3.5 (2.2-5.7) for birth before 33 weeks of gestation, and 1.7 (1.5-1.9) for cesarean delivery in singleton pregnancies that resulted after in vitro fertilization. Twin pregnancies obtained with in vitro fertilization, on the contrary, were similar for all outcome measures, except for the incidence of cesarean delivery (odds ratio, 1.4; 95% confidence interval, 1.2-1.7) compared with spontaneously conceived twin pregnancies. CONCLUSION: The perinatal outcome of singleton pregnancies obtained with in vitro fertilization is significantly worse than that of spontaneously conceived pregnancies, mainly because of the increased rate of preterm birth. The outcome of twin pregnancies obtained with in vitro fertilization is comparable with that of normally conceived twins. For both singleton and twin pregnancies obtained with in vitro fertilization, the incidence of cesarean delivery is increased.