Oral contraceptives taken before or during pregnancy are not likely to cause birth defects, according to a large-scale study investigating Denmark live births from Jan. 1, 1997 to March 31, 2011. The study was conducted by researchers from Harvard T.H. Chan School of Public Health and the Statens Serum Institut.
The researchers found that birth defects consistently occurred in 25 out of 1,000 live births regardless of whether or not the women took oral contraceptives.
"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 study author Brittany Charlton said in a news release. "This should reassure women as well as their health care providers."
The researchers studied 880,694 live births and did a follow-up on the health of the infants after a year. Around 20 percent of the mothers never used the pill before they got pregnant, while an estimated 66 percent had quit using the pill at least three months before they got pregnant. Eight percent of the women had stopped oral contraceptive use within three months of their pregnancy. One percent continued using the pill after they conceived.
The study findings showed that the prevalence of birth defects did not change across all categories of using oral contraceptives. Even when the researchers took into account the induced abortions and stillbirths, the rate remained the same.
"We did not observe a significantly increased risk of major birth defects associated with oral contraceptive use in the months before or after pregnancy onset," the authors wrote. "For women who have a breakthrough pregnancy during oral contraceptive use or even intentionally become pregnant within a few months of stopping oral contraceptive use, any exposure is unlikely to cause her fetus to develop a major birth defect."
The study was published online Jan. 6 in BMJ.
