Obstetric outcome

Pregnancy outcome after in vitro fertilization (IVF) is influenced by many factors, some specific to IVF pregnancies and others shared with the general obstetric population. These factors include the characteristics of infertile couples and their underlying causes of infertility, the criteria used by IVF programmes for selecting couples for treatment, the techniques of fertilization and embryo transfer, the management of the early stages of pregnancy and the high incidence of multiple pregnancy. In comparing outcomes in different IVF programmes or with naturally conceived pregnancies, careful attention must be given to definitions and to the methods used to diagnose pregnancies. Very few studies of pregnancy outcome after IVF have been published so far. The incidence of ectopic pregnancy and spontaneous abortion seems higher than in natural pregnancies. Multiple pregnancy is common in those programmes electing to transfer more than one embryo into the uterus. In one study, preterm birth and low birthweight were about three times more common than in population-based figures. As a result, higher perinatal mortality would also be expected, but no studies are yet available. The sex ratio and the incidence of major congenital malformations appear similar to natural pregnancies, but there are insufficient data to determine whether the risks of chromosomal abnormalities are altered in IVF pregnancies. Further studies are needed to confirm these preliminary results, to obtain better information about the occurrence of chromosomal abnormalities in spontaneous abortions, and to assess fetal growth. Comparisons of results would be enhanced by international agreement on terminology and definitions for pregnancy losses, particularly those occurring in the early stages of pregnancy. Couples considering in vitro fertilization as an option for treatment of their infertility should be counselled about their overall chances of achieving a pregnancy and live births, as well as about the outcome of these pregnancies.