Tubal sterilization less effective than previously thought

More than 5 percent of women who get their tubes tied later become pregnant, a new analysis suggests — and researchers say the failure of tubal sterilization procedures, which are widely considered permanent, “may be considerably more common than many expect.”

The study, published in NEJM Evidence, used data from the National Survey of Family Growth, which looks at contraception use, pregnancy and birth outcomes among a representative sample of U.S. women aged 15 to 44. The data was assembled during four waves of data collection from about 4,000 women who had tubal ligations between 2002 and 2015.

Most of the women surveyed reported opting for the procedure postpartum out of a desire not to have more children.

Other analyses of National Survey of Family Growth data have found that tubal sterilization, also known as having one’s tubes tied, is the most popular method of “permanent” sterilization, used by 22.4 percent of women of reproductive age in 2016. Despite such wide use, however, the researchers in the current study found “nontrivial rates of pregnancy” after such procedures.

Between 2.9 and 5.2 percent of the women studied reported getting pregnant after a tubal sterilization procedure, and between 12.1 and 32.6 percent of participants reported an ectopic pregnancy. Those who got postpartum procedures were least likely to report a subsequent pregnancy after tubal sterilization, and older patients were less likely to report a pregnancy after the procedure than their younger counterparts.

Demographic factors like Medicaid status, race/ethnicity, educational attainment, or living in a metropolitan area were not associated with higher sterilization failure rates. Nor were diabetes or obesity.

The pregnancy rates after tubal sterilization “were not trivial and may be considerably more common than many expect,” the researchers write.

“When choosing what birth control will work best for them, people consider many different things, including safety, convenience, and how fast they can start to use the method,” says Eleanor Bimla Schwarz, chief of the UCSF Division of General Internal Medicine at Zuckerberg San Francisco General and the study’s first author, in a news release. “This study shows that tubal surgery cannot be considered the best way to prevent pregnancy. People using a contraceptive arm implant or an IUD are less likely to become pregnant than those who have their tubes tied.”

The researchers call for more inquiry into the “real-world effectiveness” of different forms of contraception.

Pregnancy after tubal sterilization in the United States, 2002-2015

NEJM Evidence