Some effects of diazepam on pregnancy in the Balb/C mouse.

Female Balb/C mice aged 60 to 72 days were mated with males aged 60 to 150 days and conception was diagnosed when a vaginal plug was noted. Females were randomized into five groups, Group A animals were fed a mixture of diazepam-propylene glycol which contained 0.02 mg. of diazepam in 0.1 ml. solution per day from day 1 to 9 of the gestation. Group B animals were fed the same mixture on days 5 to 12 of the gestation. Groups C and D animals were fed 0.1 ml. of propylene glycol on gestational days 1 to 9 and 5 to 12, respectively. Group E animals served as pure controls and were fed no drug or vehicle. All animals were killed on pregnancy day 15; All pups were counted, weighed, and studied grossly for anomalies. All uteri were scored for absorption sites. Nonpregnant uteri were studied histologically and scored for day of estrogen cycle. Animals fed diazepam on days 5 to 12 of gestation (Group B) had a significantly fewer number of pregnancies than did the other groups (p smaller than 0.001). In addition, pups delivered of diazepam-fed mice were heavier than control animals. No significant differences were noted, however, with respect to litter size, number of resorption sites, or presence of gross anomalies. In view of these data it would seem prudent to continue to avoid the use of diazepam during pregnancy.