The Pill: Harmful in Early Pregnancy?

Oral contraceptives taken just before, during pregnancy not linked to higher birth defect risk

/ Author:  / Reviewed by: Beth Bolt, RPh

(RxWiki News) Could taking birth control pills while pregnant harm a developing baby? It's unlikely, new evidence suggests.

Oral contraceptives taken just before or during pregnancy were not linked to a higher risk of major birth defects, a new study from Harvard T. H. Chan School of Public Health and the Statens Serum Institute in Denmark found.

"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," said lead study author Brittany Charlton, ScD, an instructor at Harvard Medical School and Boston Children's Hospital, in a press release. "This should reassure women as well as their health care providers."

Oral contraceptives are one of the most common forms of birth control used worldwide. But despite being 99 percent effective when correctly used, nearly 10 percent of women become pregnant within their first year of use. Many more stop use shortly before conceiving.

In spite of this, little is known about the potential health effects these drugs may have on developing babies.

To investigate, Dr. Charlton and team used data from several Danish health registries to look at 880,694 babies born between 1997 and 2011. Oral contraceptive use was estimated based on the date of the mother's most recently filled prescription.

Of these babies, 2.5 percent developed a major birth defect by age 1. Babies with birth defects with known causes, such as fetal alcohol syndrome, were excluded from this calculation.

About 68 percent of mothers stopped oral contraceptive use more than three months before pregnancy, 8 percent stopped use less than three months before pregnancy and 1 percent continued use beyond pregnancy. Another 21 percent never used oral contraceptives.

After accounting for other risk factors, Dr. Charlton and team found that the rate of birth defects was consistent across all groups — regardless of oral contraceptive use.

This study was published online Jan. 6 in the journal The BMJ.

The Harvard T. H. Chan School of Public Health, the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the National Institutes of Health funded this research.

No conflicts of interest were disclosed.

Reviewed by: 
Review Date: 
January 6, 2016
Last Updated:
January 7, 2016