Solanum lycocarpum, St. Hil (Solanaceae) is a common native shrub in the Brazilian cerrado. The fruits are used in folk medicine as a hypoglycaemic agent in the management of diabetes, obesity and to decrease cholesterol levels. In this study the glycoalkaloids, solamargine and solasonine, were isolated from unripe fruits of S. lycocarpum. To evaluate the effects of the fruits on gestation, pregnant rats (n=25) were fed from day 6 to 22 with chow containing 10% of dried and ground unripe fruits. The control group (n=21) received regular chow. During and after the treatment period the dams showed reduced body weight and slower body weight gain, even with no change in food and water intake, evidencing mild maternal toxicity. Gestation was not significantly impaired, although experimental fetuses presented reduced body length at birth. Also, 20% of the treated dams showed one or two dead pups at birth. On day 22 of gestation and on post-natal day 1, the levels of metabolites of the sex hormones oestradiol, progesterone and testosterone were measured in faeces by radioimmunoassay. On post-natal day 1, tissue portions from the dams were collected for histopathological evaluation. No alterations were detected in either study. The results suggest that S. lycocarpum fruit did not impair gestation, however, it did promote mild maternal toxicity and mild fetotoxic effects if ingested as a food source during the gestation period. This study has implications for pregnant women, who employ phytotherapeutic formulations under the impression that they are harmless.