Pregnancy Rates After Tubal Sterilization: New Data Shows More Cases Than Expected

"Following tubal sterilization, 2.9% to 5.2% of women reported becoming pregnant in four separate survey waves. In the latest survey period (2013-2015), the estimated failure rate at one year was 2.9%, while the failure rate at ten years was 8.4%," the researchers reported in NEJM Evidence.

Tubal sterilization, a popular form of permanent contraception, is designed to prevent pregnancy by blocking or sealing the fallopian tubes. It is generally considered a highly effective method of contraception, with a success rate exceeding 99%. Tubal sterilization is the most prevalent form of contraception in the United States.

Given that the effectiveness of contraceptive methods affects their choice, Eleanor Bimla Schwarz, Division of General Internal Medicine, Department of Medicine, University of California, San Francisco, San Francisco, and colleagues investigated the typical use failure rates of tubal sterilization in the U.S.

For this purpose, the researchers estimated pregnancy rates following tubal sterilization by analyzing data from four waves of the National Survey of Family Growth (NSFG). This data, collected from representative samples of U.S. women aged 15 to 44 years in 2002, 2006 to 2010, 2011 to 2013, and 2013 to 2015, was used to assess the time to first pregnancy after tubal sterilization.

The researchers employed survey weighting in survival analysis to account for various factors and censored data from participants who underwent tubal reversal, infertility treatments, hysterectomy, or bilateral oophorectomy. Kaplan–Meier curves and multivariable Cox proportional-hazards models were used to examine pregnancy rates, considering variables such as age at sterilization, race/ethnicity, education, Medicaid funding, and whether the procedure was performed postpartum or at another time.

The following were the key findings of the study:

• 2.9 to 5.2% of participants reported pregnancy after tubal sterilization across NSFG waves.
• In the most recent survey wave (2013 to 2015), the estimated percentage of participants with pregnancies within the first 12 months after a tubal sterilization procedure was 2.9%; at 120 months after tubal sterilization, the estimated percentage with pregnancy was 8.4%.
• 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.
• In multivariable models, the chance of pregnancy decreased with age at the time of tubal sterilization.
• Race/ethnicity, education, and Medicaid funding were not consistently associated with pregnancy after tubal sterilization.

"These data indicate that pregnancy rates after tubal sterilization may be higher than previously anticipated," the researchers concluded.

Reference:

Schwarz EB, et al "Pregnancy after tubal sterilization in the United States, 2002 to 2015" NEJM Evid 2024; DOI: 10.1056/EVIDoa2400023.