The fetotoxic effects of maternal exposure to dichloromethane (75092) (DCM) were studied. Pregnant female rats were exposed either to filtered air or 4,500 parts per million DCM for 6 hours a day, 7 days a week, in four treatment groups: DCM exposure before and during gestation (group I); DCM exposure before gestation and filtered air during gestation (group II); filtered air before gestation and DCM during gestation (group III); and filtered air before and during gestation (group IV). Maternal liver weights were increased, and fetal body weights were decreased in groups I and III. There was no increased incidence of maternal or fetal toxicity in group I compared to group III. No effects were noted in groups II or IV. The incidence of gross external, skeletal, or soft tissue anomalies was not significantly increased in fetuses from any group. The authors note that the exposure regimen used is a realistic simulation of industrial exposure, since working women ordinarily are exposed to chemicals before and during pregnancy. Agents such as DCM that fail to induce observable teratologic effects on term fetuses can severly impair postnatal functions. A reexamination of the conventional methods of teratogenicity testing is recommended to improve their sensitivity and predictive value.