Effects of delta 9-THC on pregnancy and offspring in rats.

Pregnant rats were intubated with increasing doses of delta 9-THC (5-50 mg/kg/day) up to gestation day 5. On gestation day 5, these animals continued to receive either 50 or 150 mg/kg/day of delta 9-THC. Animals receiving the 50 mg/kg/day dose and a control group of vehicle (olive oil) treated animals were pair-fed and pair- watered to animals given the 150 mg/kg/day dose. A second control group served as nontreated, ad lib control animals. Animals were tested postnatally for spontaneous alteration, avoidance learning and rotarod behavior to determine if delta 9-THC was behaviorally teratogenic. Drug treatments produced a dose-related decrease in pregnancies carried to term, weight gain during pregnancy, and birth weight. However, since no viable litters were born to animals in the high dose-group, their data was not included in statistical analyses. Nevertheless, the effects of drug treatment (50 mg/kg/day) were still statistically significant for weight gain during pregnancy and birth weight. Drug treatment (50 mg/kg/day) did not affect litter size or weight at 21 days of age, nor did it affect any of the behavioral tests.