Do assisted reproductive technologies cause adverse fetal outcomes?

Treatment for infertility using assisted reproductive technologies (ART) is highly successful and has been used to help a steadily growing number of couples worldwide. In 1999, in the United States, more than 86,000 treatment cycles were performed resulting in the birth of more than 30,000 babies. Despite this widespread application, few follow-up studies of children conceived through ART have been performed, and more rigorous investigation of this important issue has clearly been needed. In recent months, three studies linking ART with several complications have been published in high profile and widely read general medical journals: Schieve et al. (1) reported that singletons conceived using ART were at an increased risk for low birth weight, whereas Hansen et al. (2) suggested an increased risk of major birth defects. Finally, Stromberg et al. (3) concluded that children conceived through IVF have an increased risk of neurological problems, especially cerebral palsy.

The importance of these studies is obvious as they provide clues of possible risks associated with ART. However, they are all retrospective analyses of data collected through registries and therefore are vulnerable to biases inherent to such study design. We must be careful not to overinterpret the data by concluding that the use of ART, whether from gamete or embryo manipulation or use of medications, is the direct cause of the complications—the observed associations may simply be explained by one or more confounders, such as an underlying infertility-related condition in the treated women. This short communication is an attempt to place these three articles in proper perspective for the clinician and to provide the impetus for conducting further studies to determine the true nature of the described associations.

At the outset, it should be stated that a major weakness of all three studies is the lack of proper controls. If the aim of a study is to determine whether a cause and effect relationship exists between the process of IVF and a specific outcome (i.e., low birth weight, major birth defects, neurological problems), the appropriate control population is that of babies born to infertile women achieving pregnancies by methods other than IVF. None of the three studies specifically included such a control population.