Birth Control Pills Not Linked to Birth Defects

Good news for women who got pregnant while taking or right after stopping oral contraceptives: A new study shows the pill doesn't appear to lead to birth defects.

Birth Control Pills Not Linked to Birth Defects sylv1rob1/Shutterstock

If you take birth control pills, you won't get pregnant, right? Well, not exactly—although oral contraceptives are 99 percent effective when taken correctly, up to nine percent of women become pregnant on them because of missing a dose, taking them with other medications or even getting a stomach bug. But if you get pregnant on the pill (or shortly after stopping), could it harm your baby? A new study published in the journal The BMJ thankfully says no.

No increased risk

Researchers looked at over 800,000 births in Denmark, and compared the women who had babies with birth defects with those who didn't to see if their use of birth control pills had any effect. "Our objective was to investigate whether oral contraceptive use shortly before or during pregnancy was associated with an increased risk of major birth defects," study author Brittany Charlton, Sc.D., a researcher at the Harvard T.H. Chan School of Public Health, tells Fit Pregnancy. The data showed that 68 percent of the women had used the pill but stopped more than three months before, 21 percent had never taken it, eight percent had stopped less than three months before pregnancy, and one percent took the pill after getting pregnant. In total, 2.5 percent of the babies were born with a major birth defect—but the number was the same whether their moms had taken the pill or not. "Our main finding was that there was no increased risk of having a birth defect following oral contraceptive exposure," Charlton says.

Because birth control pills contains sex hormones, there has been concern that they could harm a baby's development in the womb if exposed, and the study authors note it's unclear how long the effects of the hormones last after stopping the pill. But hormones aren't the only issue with the pill and pregnancy. "Previous research has shown that even three months after stopping use, oral contraceptives can affect a woman's vitamin A and folate levels [by raising vitamin A and lowering folate, or folic acid], both of which are linked to birth defects," Charlton says.

Although oral contraceptives have been around for decades, surprisingly little had been known about their effects during pregnancy. The new research does support most other past studies, which have also shown no increase in birth defects, but it is noteworthy because this study group is so large and so many birth defects were analyzed at once. The researchers considered major birth defects, like cleft palate and limb defects, as well as some specific ones like gastoschisis (a hole in the abdomen) which some previous studies had suggested may be linked with use of the pill. Another boon for this study is that unlike much other research, it relied on medical and prescription records instead of surveying the women themselves. In this way, "we eliminated any bias from women inaccurately recalling their use," Charlton says.

Should you TTC right after coming off the pill?

Even with the study's reassuring findings, discuss with your doctor if you should wait a bit before trying to get pregnant after stopping birth control pills. "Health care providers may still recommend stopping oral contraceptives a few months before planning a pregnancy to ensure the offspring is not exposed to [outside] sex hormones," Charlton says, even though that may just be a precaution. "The takeaway message of our study is that women who do become pregnant either soon after stopping oral contraceptives, or even while taking them, should know that this exposure is unlikely to cause her fetus to develop a birth defect. Our findings should reassure women as well as their health care providers."