Aug. 14, 2003 -- Taking aspirin or other anti-inflammatory painkillers around the time of conception or early in pregnancy increases the risk of miscarriage by as much as 80%, according to a new study.
Although these findings need to be confirmed by further studies, researchers say that in the meantime, it may be wise for women who are trying to get pregnant to be aware of this potential risk and avoid using anti-inflammatory painkillers around conception.
Doctors already recommend that women avoid anti-inflammatory drugs during pregnancy but this study shows that taking them while trying to get pregnant may also be ill advised.
Anti-inflammatory painkillers include prescription and over-the-counter medications that contain the active ingredient ibuprofen (Advil, Motrin, and others), naproxen (Aleve), and ketoprofen (Orudis KT).
Acetaminophen is a different type of painkiller -- not anti-inflammatory -- and was not found to carry this same miscarriage risk.
The study appears in the Aug. 16 issue of the British Medical Journal.
Painkillers and Miscarriage Risk
Researchers interviewed 1,055 women who had recently become pregnant about their use of painkillers, including aspirin, other anti-inflammatory drugs, and acetaminophen (the active ingredient in Tylenol). About 5% of the women reported using anti-inflammatory painkillers around conception or early in pregnancy.
After adjusting for other risk factors for miscarriage, the researchers found that anti-inflammatory drug use increased the women's risk of miscarriage by 80%. The miscarriage risk was strongest when the painkillers were taken around the time of conception or if anti-inflammatory drug use lasted more than a week.
The miscarriage risk for aspirin use around conception or early in pregnancy was similar, but researchers say it's harder to draw conclusions because there were only a small number of aspirin users in the study.
Use of acetaminophen, which works in a different way in the body, had no affect on miscarriage risk.
Anti-Inflammatory Drugs May Interfere With Implantation
Anti-inflammatory drugs suppress inflammation in the body by blocking the production of substances called prostaglandins, and researchers suspect this function may also increase miscarriage risk.
Researcher De-Kun Li, of the Kaiser Foundation Research Institute in Oakland, Calif., and colleagues say animal studies have shown that prostaglandins are necessary for successful implantation of an embryo into the wall of the uterus. Prostaglandins are also thought to play an important role in ovulation.
The researchers say the new class of anti-inflammatory drugs known as Cox-2 inhibitors -- Bextra, Celebrex, and Vioxx -- are not recommended for use by pregnant women because of embryo implantation problems found in animal studies. But these effects have not yet been well studied in older anti-inflammatory drugs, such as ibuprofen.