Objective: The goal of this study was to determine the effects of actinomycin D on fetal growth and prostaglandin dehydrogenase activity and to determine whether these effects could be obtained by administering extracts of fetal calf serum (SS-094). Methods: Actinomycin D (7 μg/100 g body weight) was injected intraperitoneally on days 11 and 12 of pregnancy to induce growth restriction in rats. In another group, SS-094 was given (0.1 ml/100 g body weight) on days 12, 15, 17 and 19 of pregnancy, following the administration of actinomycin D. Placental prostaglandin dehydrogenase (PGDH) activity was measured on days 15 and 21 of pregnancy. Statistical analysis was performed by ANOVA and Dunnet's test. Results: In the group injected with actinomycin D, fetal weight was significantly restricted (on day 15
p &lt
0.05
on day 21
p &lt
0.01), compared to the controls, and this restriction was successfully reversed by SS-094. PGDH activity in the placenta was significantly (p &lt
0.01) decreased in growth-restricted rats and remained low even after fetal weight recovered. Conclusions: Growth restriction in pregnant rats was successfully induced by actinomycin D, and SS-094 reversed this restriction. It does not seem that prostaglandin metabolism in the placenta is responsible for growth restriction.