A new study suggests that it may be surprisingly common for women to become pregnant after undergoing “tubal ligation” – slang for permanent female sterilization.
The study, published in the New England Journal of Medicine, Evidence, looked at survey data from more than 4,000 women who reported having had a tubal ligation (the official name for a series of surgeries that clamp or remove the fallopian tubes). Researchers found that 3-5% of these women reported becoming pregnant after the procedure.
“Tubal sterilization is an important form of contraception and is the right method for some people,” said Dr. Eleanor Bimla Schwartz, an internist at the University of California, San Francisco, and the study’s lead researcher.
“All methods fail at some point, so we need to know about effective alternatives, and we probably need to accept that there will always be demand for abortion services, because even methods that are considered highly effective fail, and they don’t fail very often.”
The study has received particular attention since the U.S. Supreme Court overturned Roe v. Wade in 2022. Since then, dozens of states have banned abortions or severely restricted abortion access, leading to increased interest in permanent female sterilization among women ages 18 to 30, according to the study.
The researchers conducted the study by analyzing data from four repeats of the U.S. National Survey of Family Growth, conducted between 2002 and 2015. Of the 31,000 women surveyed, 4,184 reported having had a tubal ligation.
In these studies, 3 to 5 percent of women reported becoming pregnant after the procedure, which is higher than the rate of less than 1 percent typically cited by health care professionals and the American College of Obstetricians and Gynecologists’ estimated pregnancy rate of 18 to 37 per 1,000 women after 10 years.
The data have important weaknesses: The surveys rely on patient self-reporting, which is generally less reliable than information based on medical records, and the survey data do not ask about the type of tubal ligation procedure women believe they had had.
The researchers said that if this failure rate is accurate, it would mean that tubal ligation is less effective than long-term contraception methods such as arm implants and intrauterine devices (IUDs).
The study suggests that the timing of the surgery may be important: If tubal ligation was performed shortly after giving birth, women were less likely to report being pregnant, possibly because a woman’s reproductive organs enlarge and become more visible immediately after giving birth, Schwartz said.
Notably, women who undergo surgery at an older age are less likely to become pregnant.
The study builds on previous research on the effectiveness of tubal ligation by Bimla Schwartz, who published a study in 2022 based on more than 83,000 claims from Medi-Cal, California’s public health insurance program, Medicaid, that found that tubal ligation has a similar effectiveness rate to IUDs.
If tubal ligation were as effective as an IUD, it would also suggest that younger women in particular might consider an IUD before undergoing permanent sterilization, since it is easily reversible, the authors say. Most women do not regret the procedure, but younger women are significantly more likely to express regret than older women.
“If your number one goal is to avoid getting pregnant in the future and you’re really interested in the effectiveness of it,” Schwartz says, then an arm-mounted birth control implant is probably your best option, followed by a vasectomy, or permanent male sterilization, she says, followed by hormonal IUDs, tubal ligation, and copper IUDs.
Schwartz adds: “If you’re really interested in benefits, it’s important that you really think about all of these options and discuss them with your doctor.”