A new study discovered that pregnancy after a woman has her fallopian tubes tied – the colloquial term for permanent female surgical sterilization – is surprisingly common.
The study, published in the New England Journal of Medicine Evidence, examined survey data from more than 4,000 women who reported having tubal ligations, the formal term for a series of surgeries in which the fallopian tubes are clamped or removed. Researchers found that 3-5% of these women reported becoming pregnant after the surgery.
“Ovarian sterilization is an important form of contraception and for some people it is the right form of contraception,” said Dr. Eleanor Bimla Schwarz, an internist at the University of California, San Francisco, and lead investigator of the study.
“It’s just that every method fails at some point, so we need to know what alternatives are effective. And we probably just have to make peace with the fact that there will always be a need for abortion services, because even methods that we consider very effective fail, and not so rarely.”
The research is especially relevant because the U.S. Supreme Court overturned Roe v. Wade in 2022. Dozens of states have since banned and severely restricted access to abortion, and interest in permanent surgical sterilization of women has increased among women between the ages of 18 and 30, the research finds.
Researchers conducted the study by analyzing data from four iterations of the U.S. National Survey of Family Growth from 2002 to 2015. Of the 31,000 women who participated in the study, 4,184 reported having had their fallopian tubes tied.
In those studies, between 3 and 5% of women reported pregnancy after surgery. That’s higher than the less than 1% rate commonly cited by health care providers and the 18-37 pregnancies per 1,000 women after 10 years estimated by the American College of Obstetricians and Gynecologists.
The data have significant weaknesses: Surveys rely on patient self-reporting, which is generally less reliable than information from medical records. The survey data did not ask about the type of tubal ligation surgery women believed they had undergone.
According to the researchers, if this failure rate is correct, it would mean that tubal ligation is less effective than long-term contraceptive methods such as arm implants and IUDs.
The study did note that the timing of the surgery may matter: Women were less likely to report pregnancy after tubal ligation if the surgery was performed right after giving birth. Perhaps, Schwarz said, that’s because women’s reproductive anatomy is enlarged and more visible right after giving birth.
It is striking that the chance of pregnancy was smaller if women underwent the operation at an older age.
The work builds on Bimla Schwarz’s previous research on the effectiveness of tubal ligation. In 2022, she published research based on more than 83,000 Medi-Cal insurance claims, California’s public Medicaid health insurance program. That study found that tubal ligation about the same effectiveness rate as an IUD.
If tubal ligation is as effective as an IUD, the authors say this also implies that younger women in particular may consider an IUD before permanent surgical sterilization, because they are easily reversible. Although most women do not regret the surgery, younger women significantly more likely to express regret than older women.
“If your main goal is to not get pregnant in the future, and you’re really interested in effectiveness,” then a contraceptive arm implant is probably your best option, Schwarz said. She said vasectomy, or permanent male sterilization, comes close behind, followed by hormonal IUDs, tubal ligation and copper IUDs.
Schwarz added: “It’s important that anyone who is really interested in effectiveness has thought carefully about all of these options and talked to their doctor about them.”