THURSDAY, Aug. 29, 2024 (HealthDay News) -- Women are becoming pregnant after having their tubes tied, even though the procedure is considered a “permanent” form of birth control, a new study warns.

Between 3% and 5% of U.S. women who underwent tubal ligation later reported an unplanned pregnancy, according to findings published Aug. 27 in the journal NEJM Evidence.

That means the procedure is less effective than other forms of birth control, researchers concluded.

“This study shows that tubal surgery cannot be considered the best way to prevent pregnancy,” said lead researcher Dr. Eleanor Bimla Schwarz, chief of general internal medicine at the University of California, San Francisco (UCSF).

“People using a contraceptive arm implant or an IUD are less likely to become pregnant than those who have their tubes tied,” Schwarz added in a UCSF news release.

The findings come at a time when interest in permanent contraception has increased, thanks to the U.S. Supreme Court overturning the abortion protections of Roe v. Wade in 2022.

“Since the Dobbs decision, many more people are worried about how pregnancy may impact their health and family life,” Schwarz said. “This is especially true for patients with medical conditions like diabetes and high blood pressure that can complicate pregnancy.”

In tubal ligation, both of a woman’s fallopian tubes are blocked or cut. This prevents female eggs from traveling to the uterus, where they might be fertilized by male sperm and form a fetus.

Tubal sterilization is used by more than 21% of women ages 30 to 39, and 39% of women aged 40 or older, researchers said in background notes.

Older studies had indicated that fewer of 1% of women become pregnant following tubal ligation, the researchers noted.

To check whether that’s still true, researchers analyzed data from more than 31,000 women collected in four rounds of a national health survey between 2002 and 2015. The data included nearly 4,200 women who’d undergone tubal ligation.

Between 2013 and 2015, about 3% of women became pregnant within a year of having their tubes tied, results show.

The risk of pregnancy was highest among women who were younger at the time of their tubal ligation, researchers added.

“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,” Schwarz said.

“For people who have chosen a ‘permanent’ method, learning they got pregnant can be very distressing,” Schwarz added. “It turns out this is unfortunately a fairly common experience.” 

More information

Johns Hopkins Medicine has more on tubal ligation.

SOURCE: University of California, San Francisco, news release, Aug. 27, 2024