Serena Williams, the world’s greatest tennis player and new mother, graces the cover of Vogue magazine for February, together with her daughter, Alexis Olympia Ohanian Jr, who at three months is the youngest Vogue cover model ever. And she can already list one Grand Slam win, while still in utero.

In the cover story, Williams talks about her new life as a mom and wife, her career ambitions (the cover touts her “comeback,” although that does not seem apt, since she never went away—she just gave birth) and how motherhood will affect (as in, help) each of those things.

The piece also shares a terrifying episode, in which Williams tells the story of delivering her child, the days that followed, and how she risked dying. After an emergency C-section, Williams encountered what is an often fatal complication: Blood clots. She also had to fight to be taken seriously, Vogue reports:

The next day, while recovering in the hospital, Serena suddenly felt short of breath. Because of her history of blood clots, and because she was off her daily anticoagulant regimen due to the recent surgery, she immediately assumed she was having another pulmonary embolism. (Serena lives in fear of blood clots.) She walked out of the hospital room so her mother wouldn’t worry and told the nearest nurse, between gasps, that she needed a CT scan with contrast and IV heparin (a blood thinner) right away. The nurse thought her pain medicine might be making her confused. But Serena insisted, and soon enough a doctor was performing an ultrasound of her legs. “I was like, a Doppler? I told you, I need a CT scan and a heparin drip,” she remembers telling the team. The ultrasound revealed nothing, so they sent her for the CT, and sure enough, several small blood clots had settled in her lungs. Minutes later she was on the drip. “I was like, listen to Dr. Williams!”

That’s right, only hours after giving birth through a major surgery, Williams needed to convince the medical personnel that she was in need of care—and run them through what she needed. Though she luckily survived, Williams became one of the estimated 150,000 women in America to experience serious illness or near-death experiences around pregnancy every year. Because her history of blood clots made her aware of the symptoms, Williams was able to save her own life. Unfortunately, between 700 and 1,200 American women every year don’t live to describe the experience of giving birth.

With a shockingly high maternal-mortality rate (several times the levels of other rich countries), Williams’s story will likely sound familiar to many women and all the more to black American women, who are three times more likely to die or suffer serious illness from pregnancy-related causes than white women, with at least 40 deaths per 100,000 live births on average, compared to 14 for white mothers.

That means, a black woman in America has a higher chance of dying during or right after pregnancy than a woman in developing areas of Central Europe or Eastern Asia. What’s more, what Williams had to go through is especially revealing about the medical bias faced by black women.

According to American College of Obstetrics and gynecology, at least 46% of maternal deaths among African- American women could be prevented (versus 33% for white women), which points to a systematic dismissal of symptoms and patient complaints, and less attention paid overall. Indeed, how race bias affects the medical profession is well documented.

This is not just something that affects black mothers of lesser means. It happens even to wealthy, highly educated ones, who are acutely aware of medical symptoms. “African-American doctors, lawyers, business executives, and they still have a higher infant-mortality rate than…white women who never went to high school in the first place,” Michael Lu, a neonatal specialist who has studied the impact of discrimination in maternal and newborn health, explains in the documentary When the Bough Breaks.

Indeed, even Serena Williams, whose body, as her husband correctly notes, “is one of the greatest things on this planet,” is just another black woman when it comes to being heard in the maternity ward—and when it comes to being dismissed.