Medications used to treat rheumatoid arthritis may affect abortion rate in women

Experts estimate that 1.3 million U.S. adults have RA -- an inflammatory disease where the immune system attacks the lining of the joints causing pain, swelling, stiffness, and ultimately may lead to loss of joint function. RA can affect women during their reproductive years, placing them at risk for unplanned pregnancies. In fact, one study has shown that up to half of pregnancies in North America are unplanned, and nearly half of these unintended pregnancies are terminated.

A 2003 study by Chakravarty et al. found that while 96% of rheumatologists in the U.S. had recommended birth control to female RA patients of childbearing age who were starting MTX, only 55% followed-up with patients regarding their use of contraceptives. "Women with RA who become pregnant may have disease-specific reasons which might influence their decision to end a pregnancy. Exposure to teratogenic drugs, such as MTX, which can affect the development of the fetus, is one such reason women with RA may choose an induced abortion," explains lead author, Dr. Évelyne Vinet, from the Montreal General Hospital of the McGill University Health Centre (MUHC) in Canada.

To expand evidence of induced abortion rates in women with RA exposed to MTX, the team performed a nested case-control study using Quebec's physician billing and hospitalization databases from 1996 to 2008. Women with RA who were between the ages of 15 and 45 were identified, with cases classified as women who had an induced abortion. MTX exposure was defined as filling a prescription for the drug less than 16 weeks prior to the date of abortion.

The team identified 112 women with RA who had an induced abortion (cases) and 5855 RA controls. Close to 11% of cases and 22% of controls were exposed to MTX. Compared to the unexposed controls, women with RA who were exposed to MTX had a lower rate of induced abortions. Further analysis found a potential increase in the rate of induced abortions among women exposed to anti-TNF drugs, such as Enbrel, Humira, and Remicade.

"Our study shows that women with RA who were on MTX had lower rates of induced abortions, while those exposed to anti-TNF medications had potentially higher abortion rates" concludes Dr. Vinet. "These findings highlight the importance of research on reducing the number of unplanned pregnancies in women with RA taking MTX or TNF inhibitors. Further examination of counseling practices and contraceptive use is warranted to further reduce the need for abortions in women with RA."