Women who keep taking oral contraceptives by accident after they become pregnant should not be worried about birth defects, according to a new study.
The Pill is the most common birth control method, but there is not enough research available that looks at whether circulating sex hormones in the body affects a woman’s risk of developing a fetus with a birth defect.
Researchers analyzed almost 900,000 births and found no link between oral contraceptive use just before or during pregnancy and birth defects in babies, researchers reported in The BMJ.
“For women who do become pregnant either soon after stopping oral contraceptive use or even if they’re still taking the pill, they should know that exposure is unlikely to cause their fetus to develop a birth defect,” said the study’s lead author Brittany Charlton, of the Harvard T.H. Chan School of Public Health.
According to Reuters, nine percent of women become pregnant in their first year of taking oral contraceptives because of drug interactions, missed doses or illnesses. Others might get pregnant soon after they halt oral contraceptive ingestion or they might keep taking the pills, not knowing that they are pregnant.
In such instances, the researchers said that the fetus could be exposed to the hormones in birth control pills. And some research suggested that exposure could cause birth defects by changing vitamin A and folic acid levels; both are imperative to development.
“The literature has just been unclear,” Charlton told Reuters Health.
For the study, researchers from the United States and Denmark looked at Danish birth registers for live births delivered between January 1, 1997 and March 31, 2011 to analyze the effects of birth control use, Time reports.
During that time period, 2.5 percent of children were born with a serious birth defect, such as cleft lips or palates, spina bifida, limb problems or heart defects.
Based on data from a national prescription registry, 8 percent of mothers stopped using birth control within three months before getting pregnant. And one percent used birth control after getting pregnant.
These women did not have an increased risk of a fetus with a birth defect, compared to women who never used oral contraceptives or stopped them before getting pregnant.
The risk was 25 birth defects for every 1,000 births no matter what.
There wasn’t a higher risk of birth defects when the researchers included factors such as stillbirths or induced abortions either. “That’s especially reassuring given that our results remained consistent,” said Charlton.
She did warn that the study has some limitations, one being that some birth defects are so rare that they wouldn’t be able to test for associations with certain defects.
However, researchers did conclude that oral contraceptive exposure at the beginning of a pregnancy is not likely to cause birth defects. “Our finding should reassure women as well as their healthcare providers,” she said.