“I wouldn’t go so far as to say we understand why maternal weight is associated with” negative outcomes, says Dr. Chloe Zera, a maternal fetal medicine specialist who cares for patients during high-risk pregnancies at Beth Israel Deaconess Medical Center in Boston. “Obesity can require special care, but a majority of women with B.M.I. over 30 don’t have a complicated pregnancy and do have healthy babies.” Even when the risk for complications increases, the frequency of such events remains low. When Stanford University researchers analyzed more than 1.1 million birth records in California, they found the overall prevalence of stillbirths to be five per 1,000 deliveries. Among women with a B.M.I. above 30, the rate ranged from seven to 10 stillbirths per 1,000 deliveries — as much as a twofold increase, but still a rare event. In comparison, a 2008 evidence review of the relationship between maternal age and stillbirth risk found that thinner women over 35 were also almost twice as likely to have a stillborn delivery compared with their younger counterparts. And the Stanford study could not establish a causal relationship. Stillbirths may correlate with B.M.I. because it may be harder for doctors to detect fetal complications in bigger bodies as a result of technological limitations. Larger women may also receive less careful prenatal care. When researchers analyzed audio recordings of prenatal appointments between 22 providers and 117 pregnant women, they found that providers treating patients with higher B.M.I.s asked them fewer questions about their lifestyle habits and shared less information, according to data published in 2017 in the journal Patient Education and Counseling.

All that can be said with any confidence, according to Legro, at Penn State, is that “there is no B.M.I. cut-point above which it is absolutely unsafe to have a pregnancy.” And weight loss does not ensure a safer pregnancy. When Scandinavian researchers linked data on bariatric surgery patients with infant health outcomes, they found that women who went through such procedures were more likely to have preterm deliveries and babies who were small for their gestational age than mothers of any weight who had not undergone the surgery. “Patients are told to lose weight to have a healthy baby,” Legro says. “But it’s possible that by doing so, you may be at higher risk for complications than you were before.”

One day when Balzano was 19, she walked out of a gas station and a man in a passing car yelled, “Fat bastard!” “That was the moment when I realized my body was this problem for the entire world,” she recalls. Studies dating back to the 1960s have shown that when children are presented with pictures of other kids with various body types, they rate the fat body as the one they like the least. In 2013, Yale University researchers asked 74 study participants to read a published news article about Canadian physicians who wanted to deny fertility treatments to women with obese B.M.I.s. One-third of the study subjects read the article alongside an image of a large couple eating junk food; the rest saw the same couple sitting on a bench holding hands or no accompanying image. When researchers surveyed the readers, those who had seen the junk food were more likely than the rest to support the doctors’ decision to deny fertility treatment to such patients.

Good health is often equated with being a disciplined person, a responsible citizen, a worthier mother. And stereotypes — like the assumption that all fat people are gluttonous and willfully large — can shape our understanding of a person’s health and morality. “We all have cultural biases, and health care providers are people, too,” DeJoy says. Studies have indicated that doctors across all specialties are more likely to consider an overweight patient uncooperative, less compliant and even less intelligent than a thinner counterpart. An Australian study on prenatal health care found that doctors expressed less sympathy and approval for their larger pregnant patients. “Until I found my doula and midwife, I had never had a medical professional touch my body with compassion,” says McLellan, who identifies as a fat woman and had a healthy pregnancy. “That feels normal to a person of size.”

Weight-science researchers are aware of how that lack of compassion can have health consequences. The kind of stigma that women like McLellan and Balzano encounter throughout their lives puts fat people at higher risk for depression, anxiety and suicidal thoughts. They also have higher blood pressure and higher levels of stress hormones. And many researchers documenting these risks control for B.M.I. when they collect their data. “This tells us that it’s stigma, rather than one’s weight per se, that contributes to these adverse health outcomes,” says Rebecca Puhl, an author of the 2013 Yale study and the deputy director for the Rudd Center for Food Policy and Obesity at the University of Connecticut. “This evidence also challenges the notion that stigma will motivate people to lose weight.”

Balzano’s husband, Nick, was eager to get a second opinion right away, but it was two years before she could bring herself to see another doctor. “I couldn’t take another conversation like that,” she says. “I felt like this waste of a person.” In private, she sobbed whenever friends announced a pregnancy. Then one friend, who was also heavy, told Balzano that she’d had a good experience at Boston I.V.F. So they made an appointment. When they arrived, a concierge greeted the couple as soon as they walked in. Balzano responded by starting to cry. The place felt too slick and fancy. She was sure she would once again be deemed unfit.

The doctor listened to Balzano’s story and said she understood how emotional the situation was. But she did want Balzano to lose weight. In the meantime, she was willing to prescribe letrozole, a medication used to promote ovulation, or, if that failed, a course of intrauterine insemination. I.U.I. is a low-risk procedure done without sedation in the doctor’s office; sperm is placed inside the patient’s uterus during ovulation in order to facilitate fertilization. “But it didn’t seem like she was all that interested in that,” Nick says. “The impression I got was that nobody thinks anything besides I.V.F. will work, and they wouldn’t give Gina I.V.F.” The doctor told me she recalls that she was “certainly willing to go ahead with medication and insemination,” but says she counseled Balzano to see a maternal fetal medicine specialist to discuss the potential impact of her weight on a pregnancy. Balzano declined the letrozole: “Essentially, she was saying the same thing as the first doctor — that nothing would change until I fixed my weight.”