Birth Control Pill Use After Pregnancy Not Linked to Birth Defect Risk: Study

New research suggests that women should not worry about whether taking birth control pills just before, or during the first trimester, of pregnancy will harm the development of their unborn child, with a new study finding that there was no increased incidence of birth defects among women who used the pill while pregnant. 

In a study conducted to give clarity to a long-standing health concern, findings published last week in the medical journal The BMJ indicate that women who were on birth control just before they became pregnant and women who continued to accidentally take birth control during the first trimester of pregnancy faced no increased risk of having a child with birth defects.

The birth control pregnancy concerns stem from the use of sex hormones, known as progestins, in virtually all oral contraceptives, which are known to increase levels of vitamin A and have an effect on folic acid levels, both of which have been tied to fetal development.

Using data from Danish registries involving about 900,000 women, researchers found that the rate of major birth defects stayed virtually consistent at about 25 per 1,000 live births regardless of whether women took oral contraceptives or not. In fact, those women who used the pill during the first trimester had a slight decrease, to a rate of 24.8 major defects per 1,000 live births. However, that number is likely not statistically significant.

“Women who become pregnant either soon after stopping oral contraceptives, or even while taking them, should know that this exposure is unlikely to cause their fetus to develop a birth defect,” lead author Brittany Charlton, a researcher from the Harvard Chan School Department of Epidemiology, said in a press release. “This should reassure women as well as their health care providers.”

Birth Control Pill Health Concerns

The findings are good news that follow a number of recent studies that have raised questions about the side effects of birth control pills among the women taking them.

In May 2015, researchers from the U.K. published a study, also in The BMJ, that found that women who take the newer generation of birth control pills, such as Yaz and Yasmin, appear to face a higher risk of blood clots than those who take older formulations. That study appeared to confirm findings four years earlier by the FDA and Danish researchers who reached similar findings in 2011.

A study published about a year ago in the British Journal of Clinical Pharmacology warned that long-term use of birth control pills appeared to nearly double the risk of developing brain tumors.

Birth control pills are the most widely used form of contraceptive. While they are considered 99% effective with perfect use, about 9% of women who use them within their first year become pregnant due to missed pills and other factors.