A sweeping government study of thousands of women has found links between birth defects and the older antidepressants Prozac and Paxil but has cleared other popular treatments in the class, including Celexa, Lexapro and Pfizer's Zoloft, which is the subject of a major lawsuit over birth defect claims.
Earlier studies had raised questions about antidepressants in a class of drugs known as selective serotonin reuptake inhibitors, or SSRIs, prompting the U.S. Food and Drug Administration in 2005 to issue a safety warning about use of the treatments during pregnancy.
A June report published in the Journal of the American Medical Association found a slightly elevated risk for babies born with persistent pulmonary hypertension of the newborn when their mothers took antidepressants during the 90 days before delivery.
In the current study, published this week in The British Medical Journal, researchers at the U.S. Centers for Disease Control and Prevention wanted to see if the birth defect risk affected the entire class of drugs or only select treatments.
For the study, the researchers asked nearly 28,000 women if they took Celexa, Lexapro, Prozac, Paxil or Zoloft at any time from one month before conception through the third month of pregnancy. It analyzed which women bore children with birth defects.
They found that the popular antidepressants Celexa, Lexapro and Zoloft are not associated with birth defects. Only two in the study — Prozac, sold generically as fluoxetine, and Paxil, sold generically as paroxetine — were implicated.
Among women who took those two drugs early in pregnancy, birth defects occurred two to three and a half times as often as among women who did not take them.
Prozac use was associated with a birth defect in which a baby's skull is misshapen. Paxil use was associated with a defect in which a baby's intestines protrude outside the body and with anencephaly, in which a baby is missing parts of the brain and skull, the study found.
Both Paxil and Prozac were linked to a heart defect.
The study's authors noted that the risks appeared small. For example, in women who took paroxetine early in pregnancy, the risk for anencephaly rose from 2 cases per 10,000 to 7 per 10,000.
The analysis was able to show links only between the drugs and birth defects but could not prove that the drugs caused the deformities.
The authors called the findings about Zoloft “reassuring” because the drug was used by some 40 percent of the women in the study who said they used an antidepressant in early pregnancy.