Methotrexate is a medication used to treat rheumatoid arthritis. The drug is known to cause fetal malformations and birth defects, but researchers claim abortion rates are higher in women not treated with the drug than women on methotrexate at pregnancy. Researchers suggest multiple scenarios as possible causes for reduced elective abortion rates. The study results and theories were published in an April 2013 edition of Arthritis Care & Research.

Methotrexate is known to cause microcephaly, skeletal abnormalities and hydrocephalus. Due to the possible fetal complications, some women being treated with the drug for rheumatoid arthritis (RA) choose to abort the fetus if pregnancy occurs during treatment. While it is known that induced abortions are associated with treatment, researchers had little idea just how many abortions were taking place.

Of the nearly 6,000 pregnancies in women with RA, 112 abortions were reported. A control group of women with RA but no methotrexate exposure were also investigated for the study. About 11% of induced abortions occurred in women exposed to methotrexate. That number rose to nearly 22% in women not exposed to the drug. Women with RA who were exposed to anti-TNF (tumor necrosis factor) reported more abortions than women exposed to methotrexate though anti-TNF is not associated with fetal malformations. Researchers believe women being treated with anti-TNF may be misinformed about the possible side effects of taking the drug.

The study results reported a higher number of abortions in women with RA compared to other studies. Typically, abortion rates for women with RA are about half of the normal population rate. Researchers believe there could be a missing link in education for women being treated with methotrexate accounting for the increased number of unintended pregnancies and subsequent abortions.

Contraception use should be stressed for women with RA being treated with methotrexate. Education includes consultation initially, prior to beginning treatment and continued education about the importance of preventing pregnancy while using the rug. It can take up to 12 weeks for the drug to be pushed completely out of the body after treatment concludes. Contraception use needs to be continued during this period.

Source: Evelyne Vinet MD, Bindee Kuriya MD, MSc, Christian A. Pineau MD, Ann E. Clarke MD, MSc, Sasha Bernatsky MD, PhD. Induced abortions in women with rheumatoid arthritis on methotrexate. Arthritis Care & Research. 2013 April 16. DOI: 10.1002/acr.22000.

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