Background: The effects of taking oral contraceptive pills that contain steroid hormones (estrogen and progesterone) during pregnancy on some aspects of fetus and newborn have been previously reviewed. Objectives: The objectives of this study are to detect the effect of using different doses of progestin and estrogen (contraceptive pills OCPs) by pregnant female mice on the gonadal development of their male fetuses, and on their pregnancy outcome. Materials and Methods: Ninety female mice were divided equally into three major groups: two experimental (G1 and G2) and control group according to the level of the dose. Administration of OCPs (either 0.034 or 0.068 mg/kg b. wt. /d dissolved with 0.1ml distilled water) orally once a day, were started at the first day of gestation and continued till day 14 for the experimental groups G1 and G2 respectively. When the female in each experimental and control groups reach day 17 of gestation, 15 animals of each group were sacrificed, whereas the other 15 animals were left to be sacrificed at birth time. Weight and numbers of fetuses were recorded, in addition, histological study for their testes were done. Results: The statistical analysis showed a highly significant (P<0.01) decrease in weights and numbers of fetuses (males and females), and highly significant decrease ( (P<0.01) in the testes diameter of fetuses belonged to mothers treated with normal and double dose of OCPs at day 17 and at birth time. In addition, fetuses belongs to G2 mothers revealed testicular undescending to its normal position and remained adjacent to the kidneys at the upper part of the abdominal cavity in comparison with control group. Conclusion: Administration of steroid hormones orally to pregnant female mice for 14 days causes a highly significant decrease in the weight and number of fetuses at day 17 and at birth time and cause negative effect on the diameter of the fetal testes. The OCPs can inhibit at its high dose, the descending of the testes to its normal location at the pelvic cavity and then to the inguinal canal.