Heather*, a 28-year-old from Ohio, spent four years searching for a doctor who would sterilize her. Her insurance wouldn't let her go straight to an ob/gyn without a referral, but the first three doctors she saw declined to refer her to a specialist for the consultation, raising myriad concerns: You’re too young. You’ll change your mind once your biological clock starts ticking. You’ll feel differently once you meet the right person. What if your future partner wants children?

They recommended long-acting reversible contraceptive (LARC) options, like an IUD, instead. So Heather kept asking.

When she finally secured an ob/gyn appointment, she arrived armed with a letter explaining her reasons for seeking sterilization. First, she wrote, she has no biological imperative to have kids. But if her doctor wanted “better reasons,” she had them: She has an unruptured brain aneurysm that pregnancy could worsen. She also has PTSD from past traumas that could be significantly exacerbated if she became pregnant. To her surprise, this doctor agreed to sterilize her. Heather had a successful tubal ligation three months later.

Heather is child-free, a term many use to describe not wanting children—as opposed to childless, which implies that a person may wish to have children at some point.

It's hard to know exactly how many women identify as child-free by choice (and for life). Data from the 2016 census shows that 43.4 percent of American women ages 15 to 50 don’t have children. But that doesn’t tell us how many of those women are child-free by choice. However, data from the National Health Statistics Report in 2012 also found that 43 percent of American women ages 15 to 44 were childless at the time, and of those, 6 percent reported being “voluntarily childless,” which, according to the survey, were women "who expect to have no children in their lifetimes."

Of course, not all child-free women choose sterilization as their form of birth control. For instance, Brittany Brolley, who blogs about being child-free at The Rinky-DINK Life, got a hormonal IUD last year. “Permanent birth control certainly appeals to me but I really enjoy the perks of having the Mirena,” the 28-year-old tells SELF. For some people, those perks include lighter periods, cost-effective birth control, and the ability to remove it later.

But some child-free women want permanent birth control through sterilization—a desire they often need to justify and defend.

Megan*, a 32-year-old from Canada who had her fallopian tubes surgically removed this year, says she was “laughed out of” a doctor’s office the first time she asked about sterilization. For her second appointment, she prepared a binder of documents including her personal reasons for wanting sterilization, research into post-sterilization regret, and information about the procedure. She also presented her doctor with a notarized statement that she was certain about her choice and understood the risks and permanence of the surgery.

“I didn't want to give the doctor any reason to doubt that I was serious,” she tells SELF. “I wanted to be prepared with research and rebuttals if another doctor told me that I would change my mind someday.” Megan’s second doctor agreed to carry out the surgery, and she believes that her proof of preparation—and the notarized document—made a difference.

Anjali Nowakowski, a 31-year-old attorney and writer, had two different ob/gyns tell her she was too young to get sterilized when she was in her early and late 20s. Nowakowski finally found an ob/gyn to sterilize her in 2016. “The amount that people think women can’t make their own decisions, or can’t make valid or reasonable decisions around having babies…that pisses me off to no end,” Nowakowski tells SELF.