Tubal sterilization fails often enough, study says

New research finds nontrivial rates of unintended pregnancy after tubal sterilization, which challenge the assumption that the procedure is a completely reliable form of birth control.

Data from four waves of the National Survey of Family Growth (NSFG) in the US showed that between 2.9 percent and 5.2 percent of participants who had undergone tubal sterilization had unintended pregnancies. [NEJM Evid 2024;doi:10.1056/EVIDoa2400023]

In the most recent survey wave (2013 to 2015), 2.9 percent of participants had pregnancies within the first 12 months after a tubal sterilization procedure. The estimated percentage rose to 8.4 percent at 120 months after the procedure.

“At all the time points examined, pregnancy after tubal sterilization was less common after postpartum procedures than after interval procedures; however, this difference was not evident in multivariable models,” noted the investigators who were led by Dr Eleanor Bimla Schwarz from the University of California San Francisco, San Francisco, US.

In multivariable models, women who underwent tubal sterilization at an older age had a lower chance of subsequent pregnancy. Factors such as race/ethnicity, education, and Medicaid funding did not significantly influence the likelihood of pregnancy after tubal sterilization.

“This study shows that tubal surgery cannot be considered the best way to prevent pregnancy,” Schwarz said in a news release.

“People using a contraceptive arm implant or an intrauterine device are less likely to become pregnant than those who have their tubes tied,” she added.

In the US, tubal sterilization is the most common method of contraception. The American College of Obstetricians and Gynecologists describes sterilization as a highly effective way to prevent pregnancy, with fewer than 1 in 100 women getting pregnant within 1 year of having the procedure. [https://www.acog.org/womens-health/faqs/sterilization-for-women-and-men]

“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. It turns out this is unfortunately a fairly common experience,” she added.

In the present research, Schwarz and colleagues looked at 31,000 women aged 15–44 years from the 2002, 2006–2010, 2011–2013, and 2013–2015 NSFG waves. Of the participants, 4,184 reported having undergone tubal sterilization and were included in the analysis.

Time to first pregnancy after tubal sterilization was examined using survey weighting in survival analysis. Kaplan–Meier curves and then multivariable Cox proportional-hazards models were applied to examine the effects of age at tubal sterilization, race/ethnicity, education, Medicaid funding, and postpartum versus interval procedures on reported pregnancy rates after tubal sterilization procedures.