Over-the-counter pain medications, retinoids used for dermatological conditions, and steroid drugs used to treat rheumatoid arthritis all carry a risk of causing miscarriage. Caffeine, alcohol and recreational drugs also increase a woman's risk of miscarriage.
The over-the-counter pain medications that increase miscarriage risk are the nonsteroidal anti-inflammatory drugs: ibuprofen, aspirin and naproxen, as well as prescription drugs in the same category. This drug class does not include the popular over-the-counter painkiller acetaminophen, which is not associated with miscarriage. Nonsteroidal anti-inflammatory drugs increase the risk of miscarriage by causing fluctuations in hormone levels.
Retinoids are prescription-only medications used to treat severe acne, eczema and other skin conditions. The association between retinoids and miscarriage or severe birth defects is so strong that women who take retinoids are required by the FDA to use two methods of birth control and receive regular pregnancy tests. Men who use retinoids are also required to use birth control; retinoids are excreted in semen, making the partners of men who take these drugs more likely to miscarry even if they do not take retinoids themselves.
The rheumatoid arthritis drugs misoprostol and methotrexate carry such a high risk of miscarriage that they are used to induce abortions. When used alone, misoprostol has an 88 percent effectiveness at terminating pregnancy. Its effectiveness is even higher when used with methotrexate, and these drugs must be avoided by pregnant women.