American researchers have found that rates of pregnancy after tubal sterilisation may be higher than previously expected, according to their analysis of national survey data, providing “more clarity on the procedure's real-world effectiveness”, they say.
After having tubal ligation, 2.9% to 5.2% of women later reported becoming pregnant across four different waves of the survey, reported Eleanor Schwarz, MD, of the University of California San Francisco, and colleagues in NEJM Evidence.
In the most recent survey wave (2013-2015), failure at one year was estimated to be 2.9%, while failure at 10 years was 8.4%, the researchers found.
“Because the Dobbs decision has further limited access to pregnancy termination services for many US women, information on contraceptive effectiveness is particularly salient,” they wrote.
“Women considering tubal surgery should be well-informed about options that can be safely and conveniently used for years and are likely to be more effective – including the arm implant, hormonal IUD (intrauterine device), hormone-free IUD, and vasectomy,” Schwarz told MedPage Today.
After meeting a number of women who had become pregnant after tubal sterilisation, Schwarz said she started to wonder how often it actually occurs. The American College of Obstetricians and Gynaecologists estimates that 18 to 37 of every 1 000 women still fall pregnant within 10 years of having a laparoscopic sterilisation surgery, but Schwarz said it seemed more common, based on her observations.
She and her colleagues analysed data on women aged 15-44 from the National Survey of Family Growth (NSFG), a periodic nationally representative survey that provides estimates of factors affecting pregnancy and birth outcomes, like sexual activity and contraceptive use.
They looked at four waves (2002, 2006-2010, 2011-2013, and 2013-2015), identified women who had a tubal sterilisation, and calculated the number of months that had passed between the surgery and pregnancy.
Most of the sterilisations occurred postpartum and more than half of the women had the procedure before 35. Most of the pregnancies were intrauterine, though between 12.1% and 32.6% were ectopic.
Schwarz and colleagues found in unadjusted analyses that contraceptive failure was less common after postpartum procedures than after interval procedures, but those differences disappeared in multivariable analyses.
Age at the time of tubal ligation remained a predictor of pregnancy in those multivariable analyses, with older women being considerably less likely to become pregnant after the procedure, they reported.
Funding of tubal sterilisations by Medicaid wasn’t associated with a greater likelihood of pregnancy compared with private or other insurance, they added. Nor was pregnancy after tubal sterilisation associated with race/ethnicity, educational attainment, or living in a metropolitan area.
In an accompanying editorial, Julia Tasset, MD, MPH, and Maria Rodriguez, MD, MPH, both from the Oregon Health & Science University in Portland, wrote that the study was “one of the first attempts to update clinical understanding of the effectiveness of permanent tubal contraceptive procedures in the era of modern laparoscopy”.
Most knowledge about tubal sterilisation is based on 40-year-old data from the pivotal CREST (Collaborative Review of Sterilisation) study, they wrote. Schwarz and team’s estimates of pregnancy after tubal sterilisation “are four to five times higher than estimates given in the CREST study and are higher than the typical-use risk of failure for long-acting reversible contraceptive methods, such as the intrauterine device or subdermal implant”, they said.
They also noted that these results “are surprising not only for the magnitude of difference but also in light of the shift toward interval laparoscopic permanent tubal contraception”.
In a second editorial, Hyungjin Myra Kim, ScD, of the University of Michigan, commended the authors on their study design, which can be tricky when analysing outside survey data.
“The authors designed their study to utilise existing survey data effectively and demonstrated the value of secondary data analysis based on the nationally representative survey data by careful decision-making regarding data management methodology, enabling them to derive meaningful conclusions,” Kim wrote.
Schwarz and colleagues noted a handful of limitations, including that NSFG relies on participant recall and doesn’t distinguish between the types of laparoscopic sterilisation procedures. It also does not distinguish between hysteroscopic and laparoscopic sterilisation procedures, though previous research found similar rates of effectiveness between approaches.
Additionally, some participants may not have reported pursuing assisted fertility services and NSFG data are known to underreport abortions. Also, the authors conservatively excluded the small number of women with imputed dates of conception.
Study details
Pregnancy after tubal sterilisation in the United States, 2002 to 2015
Eleanor Bimla Schwarz, Amy Yunyu Chiang, Carrie Lewis, Aileen Gariepy, and Matthew Reeves.
Published in NEJM Evidence on 27 August 2024
Abstract
Background
Tubal sterilisation is the most commonly used method of contraception in the United States. Because contraceptive effectiveness influences contraceptive selection, we examined typical use failure rates after tubal sterilisation in the US
Methods
We estimated rates of pregnancy after tubal sterilisation using data from four waves of the National Survey of Family Growth (NSFG), representative samples of US women aged 15 to 44 years, collected in 2002, 2006 to 2010, 2011 to 2013, and 2013 to 2015. Survey weighting was used in survival analysis to examine time to first pregnancy after tubal sterilisation. Data from these participants were censored after a tubal reversal procedure, infertility treatment, hysterectomy, or bilateral oophorectomy. Reported pregnancy rates after tubal sterilisation procedures were examined by using Kaplan–Meier curves and then multivariable Cox proportional-hazards models to examine the effects of age at tubal sterilisation, race/ethnicity, education, Medicaid funding, and postpartum versus interval procedures.
Results
Pregnancy after tubal sterilisation was reported by 2.9 to 5.2% of participants 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 sterilisation procedure was 2.9%; at 120 months after tubal sterilisation, the estimated percentage with a pregnancy was 8.4%. At all the time points examined, pregnancy after tubal sterilisation was less common after postpartum procedures than after interval procedures; however, this difference was not evident in multivariable models. In multivariable models, chance of pregnancy decreased with age at time of tubal sterilisation. Race/ethnicity, education, and Medicaid funding were not consistently associated with pregnancy after tubal sterilisation.
Conclusions
These data suggest that there may be nontrivial rates of pregnancy after tubal sterilisation.
See more from MedicalBrief archives:
US sterilisations double after Roe v Wade overturned
Claim against gynaecologist for tubal ligation billed but not performed
Prevent ovarian cancer by removing fallopian tubes, urge experts