This report presents the outcome of pregnancies of 93 women who conceived while taking progesterone (P) suppositories (n = 42) or P in oil intramuscularly (n = 51). The dosage and duration of treatment varied according to the indication. The total dose (in milligrams) increased with the duration of treatment and ranged from 75 to 13,500 mg. Two of 75 term pregnancies (2.6%) were noted to have congenital anomalies. Both women had been treated with P in oil. No patient treated with P suppositories gave birth to a malformed infant. An increased spontaneous abortion rate (28.6%) was noted among women treated with P suppositories. The authors recommend that a national registry be created to document fetal outcome after P therapy.