Monitoring outcomes of pregnancy following drug exposure: a company-based pregnancy registry program

Women who discover they are pregnant after exposure to a drug and pregnant women who have a condition that requires continued treatment during pregnancy are told to balance the benefits and risks of the exposure to justify continuation of treatment, discontinuation of treatment or, possibly, pregnancy termination. However, there are limited data available to inform decision-making. The Merck Pregnancy Registry Program is a company-run pregnancy registry whose objective is to acquire and analyse information on drug exposures and pregnancy outcomes to better describe the safety profile of Merck products used during pregnancy. Information is collected from women and healthcare providers who call to report drug exposure during pregnancy. Prospective pregnancies are followed up to outcome and data are collected via questionnaires, telephone calls and a review of medical records. Reports are classified as prospective (information received prior to knowledge of pregnancy outcome) or retrospective (received after the outcome is known). Congenital anomaly reports are assessed for timing of exposure, maternal age and medical history, biological plausibility and concomitant medication exposures. Rates of pregnancy outcomes and birth defects in the prospective cohort are computed and confidence intervals are calculated to reflect the strength of the finding based on the sample size. Rates of pregnancy outcomes in the Pregnancy Registry are compared with the rates of pregnancy outcomes in the general US population and, if available, in subpopulations with the relevant disease states. The limitations of post-marketing surveillance are well known as voluntary reporting of individuals and healthcare professionals is known to be subject to various types of bias. Small sample size is another major limitation. However, the strength of the registry lies in its ability to gather pregnancy outcome reports early in the life of a product and to recognise and analyse unusual birth defects. Our data suggest that pregnancy registries can be used to review human exposure data in a systematic fashion so that useful information can be shared with women and their healthcare providers. The use of the pregnancy registry design has allowed for the collection and analysis of data on the effects of drug exposures on human pregnancies that have otherwise been difficult to obtain.