Jan. 13, 2012

By Patricia Nicholson

A new study comparing birth control pills in breastfeeding women found that the type of pill they took had no effect on whether they continued breastfeeding or whether they continued taking the pill, and also had no effect on the growth of their babies.

The study authors explain that breastfeeding women are commonly prescribed progestin-only birth control pills, rather than pills that contain both progestin and estrogen. This choice is often made out of concern that estrogen might slow down the production of breast milk, which could result in the mother giving up breastfeeding early, or in poor infant growth. However, in women who are not breastfeeding, the usual choice of birth control pill is a combination pill because they often have fewer side-effects, may be more effective, and women may be less likely to stop using them.

To find out if pill choice affected breastfeeding, researchers at the University of New Mexico, Albuquerque designed a study involving 127 breastfeeding women who were randomly assigned to either progestin-only birth control pills or combination pills two weeks after giving birth. They followed the women for six months. The women answered questions about breastfeeding and birth control two weeks after they started taking the pill, and again eight weeks after the study began. The researchers also followed up with phone calls to the participants several weeks into the study, after four months and again after six months.

The results showed that there were no differences between the two groups in the number of women who continued to breastfeed: in both cases, about two-thirds of the participants continued to breastfeed. The researchers also found no differences between the progestin-only group and combination pill group in the number of women who continued using the prescribed pills, or in the growth of their babies. 

These findings suggest that neither type of birth control pill appears to have adverse affects on breastfeeding.

The study was published in the January issue of Obstetrics & Gynecology.