The objective of this study was to characterize the adverse effects of Ahnjon-Yichun-Tang during early pregnancy. Following successful mating, female Sprague-Dawley rats were given Ahnjon-Yichun-Tang(AYT) extract by oral administration daily with dose of 150mg (n=10), 300mg(n=10), 450mg(n=10) for 20 days of pregnancy. The rats in Control group(n=10) were orally administrated with Saline. All pregnant rats of Ahnjon-Yichun-Tang-treated and Control groups were sacrificed on day 20 of pregnancy. The pregnancy outcome was determined and the internal and reproductive organs of pregnant rat were observed. The fetuses were examined for the presence of various developmental toxic endpoints and stained with alcian blue and alizarin red S, and observed skeletal malformations. The results obtained in this study represent that there is no significant changes between Control and Ahnjon-Yichun-Tang-treated groups in body weight, organ weight, blood chemistry values, hematological values and pregnancy indexes of pregnant rat. The skeletal malformation of fetus was not observed as well. These results suggest that oral administration of Ahnjon-Yichun-Tang does not produce either maternal or developmental toxicity.