Most women in the U.S. between the ages of 15 and 49 use contraception, according to federal data released Wednesday — and the most common form is permanent.

According to the new report from the National Center for Health Statistics (NCHS), which polled women from 2015 to 2017, sterilization was the most common contraceptive method for the roughly 47 million women in this age range. Almost 19% of women relied on female sterilization — a permanent procedure that involves either cutting, sealing, tying or manually blocking the fallopian tubes — for birth control.

Almost 13% of women said they used birth control pills, followed by about 10% who used long-acting reversible contraceptives (LARCs) such as intrauterine devices (IUDs). Almost 9% of women used the male condom for birth control, and almost 6% relied on a male parter’s sterilization, which is performed through a vasectomy. Smaller proportions of women used methods including rings, patches, diaphragms and injections.

Female sterilization is most common among older women. Since the procedure is irreversible, doctors usually recommend it only to women who are finished having children or know they do not want to at any point. About 40% of women ages 40 to 49 rely on female sterilization for birth control, according to the report — which may partially explain why women in this age group were the most likely to be using any type of contraception, along with factors like not wishing to expand existing families.

Pills, meanwhile, were more commonly used by women in their teens and twenties than by older women. LARCs and condoms were more popular among women in their twenties and thirties than those in their teens or forties.

Teen birth rates are at a record low — but contraception use in this age bracket is also fairly low, the report showed. Just 37% of women ages 15 to 19 said they were using contraception.

The latest numbers represent a slight overall increase in contraception use. Almost 65% of women in the survey said they used contraception, but that number was around 62% between 2002 and 2015. The uptick can be partially explained by surveying methods: The new report was based on more than 5,500 responses to the 2015-2017 National Survey of Family Growth, which for the first time expanded its age range to include women aged 45 to 49, a demographic with high rates of contraception use.

Other possible explanations include expanded access to birth control under the Affordable Care Act, changing attitudes toward having children and the increasing popularity of permanent and long-term options like female sterilization and IUDs.

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Write to Jamie Ducharme at jamie.ducharme@time.com.