Diethylstilbestrol (DES) is a medicine that was prescribed in Canada and the United States from 1948 to 1971 to prevent miscarriage or premature delivery. It is no longer prescribed, because it was found to cause various medical problems in the children of the women who used it.

Daughters born to women who took DES while pregnant have a slightly higher risk for:

• Abnormal cervical cells that cause an abnormal Pap test.
• Cancer of the cervix or vagina.
• Structural problems in their reproductive organs, such as a T-shaped uterus or a weakened cervix, which can cause infertility and a higher risk for preterm labour.

Sons born to women who took DES while pregnant have a slightly higher risk of abnormalities of the scrotum and decreased sperm counts.