Maternal factors, medications, and drug exposure in congenital limb reduction defects.

As part of an ongoing study on all limb reduction defects occurring among 1,213,913 consecutive live births in the province of British Columbia, Canada, during 1952-1984, cases with documented maternal drug exposure and chronic maternal diseases were analyzed separately. This population-based study was made possible through the existence of an ongoing Health Surveillance Registry, which documents all infants born with congenital, genetic, or chronically handicapping conditions in the province of British Columbia. Strict rules of confidentiality are obeyed. For this part of the analysis of limb reduction defects, cases with documented maternal illness, drug abuse, and exposure to environmental hazards early in pregnancy were analyzed as a separate group to identify specific, recurring patterns of anomalies. A total of 51 cases with possibly related maternal factors were identified. Among them were five cases with maternal epilepsy, four cases with documented maternal diabetes, and three cases with uterine anomalies. Three infants, all born in 1962, had documented thalidomide exposure. It is rarely possible to identify particular teratogenic factors or specific maternal factors as etiologically related to the pattern of limb reduction defects or a spectrum of congenital malformations. Exposure to environmental factors during pregnancy is not reliably registered and can thus only occasionally be ascertained in retrospective studies. This means that very large numbers of cases and cross-referencing to other family members are required to assess whether a potential teratogen is related to limb defects or not.