A sweeping government study of thousands of women has found links between the older antidepressants Prozac and Paxil and birth defects 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 re-uptake inhibitors (SSRIs), prompting the U.S. Food and Drug Administration in 2005 to issue a safety warning about use of the treatments during pregnancy.

In the current study, published on Wednesday 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.