A new study published in the American College of Rheumatology (ACR) journal, Arthritis Care & Research, suggests that medications used to treat rheumatoid arthritis may affect abortion rates in women.  Some drugs used to treat RA, such as methotrexate, may be harmful to a developing fetus.  

In North America, up to 50% of pregnancies are unplanned and that nearly half of unintended pregnancies are terminated (Winner, 2012).  Rheumatoid arthritis, which is more common in women than men, can affect individuals during their reproductive years, putting them at risk for unplanned pregnancies.

Patients who begin treatment with methotrexate are advised to use effective birth control.  In fact, it is recommended that a patient stops using methotrexate (MTX) at least 3 months before trying to get pregnant.  A recent survey revealed that 96% of rheumatologists in the U.S. regularly discuss birth control with RA patients of childbearing age who are starting MTX.  However, only 55% routinely follow-up with their patients regarding use of contraceptives (Chakravarty, 2003).

Researchers in Quebec wanted to know if induced abortions were more common in RA patients who were exposed to methotrexate.  Led by Dr. Evelyne Vinet from the Montreal General Hospital of McGill University Health Centre, researchers conducted a nested case-control study using Quebec’s databases of physician billing and hospitalization codes from 1996 to 2008.  All women living with RA between the ages of 15 and 45 were identified and cases were defined as women having an induced abortion.

Researchers identified 112 women with RA who had had an abortion.  For each case, age-matched controls (n=5855) were selected at random from all subjects who entered the cohort on the same month and year as their corresponding study case, and who were born within 12 months of the case’s birthdate.  Women who were not at risk of becoming pregnant due to use of an IUD, surgical procedure or any other cause, were excluded.  

Only women who had continuous public drug coverage during the 4 months before study entry were included.  Exposure to methotrexate was defined as having filled at least one prescription of MTX in the 16 weeks prior to study entry.  Researchers also identified exposure to other drugs, including anti-TNF medications and prednisone, as well as number of physician or hospital visits in the previous year.

Of the 112 women who had an induced abortion,  10.7% had been exposed to MTX (n=12), 6.3% exposed to anti-TNF medication (n=7), and 10.7% exposed to prednisone (n=12).  In the control study group, 21.7% had been exposed to MTX (n=1272), 3.1% exposed to anti-TNF medication (n=179), and 16.4% exposed to prednisone (n=960). The overall rate of induced abortion observed in women with RA was half the rate of the general population.

In this study, women exposed to MTX had a lower rate (aRR 0.47) of induced abortions compared to unexposed women.  Possible reasons for this lower rate may be the use of effective contraception leading to fewer unplanned pregnancies or less sex due to increased disease activity.  Also, spontaneous abortions (miscarriages) may be increased in women who use MTX (Lloyd, 1999), resulting in a lower induced abortion rate.