During my pregnancies (back in the early 90s), there were lots of medications my doctor told me to avoid—but if I needed relief from aches and pains, I heard, it was OK to take a nonsteroidal anti-inflammatory drug (NSAID). But: That could have had tragic consequences—because a large new study suggests that taking NSAIDs during pregnancy can more than double a woman’s risk for miscarriage. This is a significant finding in an area that has shown inconsistent research results. So if you are expecting or know someone who is, please take note and spread the word.

Background: In the US, nonprescription NSAIDs include ibuprofen (Advil, Motrin) and naproxen (Aleve)…in Quebec, Canada (where the new study was done), ibuprofen is the only nonprescription NSAID. In both countries, prescription-strength NSAIDs include ibuprofen, naproxen, diclofenac (Voltaren) and celecoxib (Celebrex). NSAIDs are among the most commonly used medications during pregnancy, taken by an estimated 17% of expectant mothers. Here’s what researchers found…

The new study involved 4,705 women who miscarried prior to the 20th week of pregnancy, plus a control group of an additional 47,050 women who did not miscarry. Researchers based their analysis of NSAID use on whether each woman had filled a prescription for such a drug immediately prior to or in the first 20 weeks of her pregnancy. Results: Women who filled one or more prescriptions for NSAIDs were 2.4 times more likely to suffer miscarriages than women who had not received the medication. Though researchers had no way of knowing exactly how much of the medication each woman actually took, miscarriage risk appeared to be elevated no matter what NSAID dosage was prescribed.

Theory: NSAIDs may interfere with hormonelike substances in the uterine lining that affect a woman’s ability to maintain a pregnancy. Why might this study be more reliable than previous ones? Because it included a very large number of women…miscarriage diagnoses were confirmed by physicians…and the data on NSAID use were based on actual prescriptions filled and not just on patient recall. Though this study included only NSAIDs purchased by prescription, researchers pointed out that participants could have received prescriptions for nonprescription-strength formulations…and that the purchase of nonprescription NSAIDs would have been equally likely among participants who did miscarry and those who did not miscarry, so this would not have significantly altered the study findings.

Bottom line: Researchers warn that any NSAID use during early pregnancy may increase the risk for miscarriage. Aspirin also should be avoided unless specifically recommended by your doctor because it increases the risk for bleeding. If you need pain relief during pregnancy: Ask your doctor if it is OK for you to take acetaminophen (Tylenol), which is not an NSAID (though it can damage the liver if used improperly).