Charity Watkins sensed something was deeply wrong when she experienced exhaustion after her daughter was born.

At times, Watkins, then 30, had to stop on the stairway to catch her breath. Her obstetrician said postpartum depression likely caused the weakness and fatigue. When Watkins, who is Black, complained of a cough, her doctor blamed the flu.

About eight weeks after delivery, Watkins thought she was having a heart attack, and her husband took her to the emergency room. After a 5½-hour wait in a North Carolina hospital, she returned home to nurse her baby without seeing a doctor.

When a physician finally examined Watkins three days later, he immediately noticed her legs and stomach were swollen, a sign that her body was retaining fluid. After a chest X-ray, the doctor diagnosed her with heart failure, a serious condition in which the heart becomes too weak to adequately pump oxygen-rich blood to organs throughout the body. Watkins spent two weeks in intensive care.

She said a cardiologist later told her, “We almost lost you.”

Watkins is among 12 million adults misdiagnosed every year in the United States.

In a study published January 8 in JAMA Internal Medicine, researchers found that nearly 1 in 4 hospital patients who died or were transferred to intensive care had experienced a diagnostic error. Nearly 18 percent of misdiagnosed patients were harmed or died.

In all, an estimated 795,000 patients a year die or are permanently disabled because of misdiagnosis, according to a study published in July in the BMJ Quality & Safety periodical.

Some patients are at higher risk than others.

Women and racial and ethnic minorities are 20 percent to 30 percent more likely than White men to experience a misdiagnosis, said David Newman-Toker, a professor of neurology at Johns Hopkins School of Medicine and the lead author of the BMJ study. “That’s significant and inexcusable,” he said.

Researchers call misdiagnosis an urgent public health problem. The study found that rates of misdiagnosis range from 1.5 percent of heart attacks to 17.5 percent of strokes and 22.5 percent of lung cancers.

Weakening of the heart muscle — which led to Watkins’ heart failure — is the most common cause of pregnancy-realted death one week to one year after delivery, and is more common among Black women.

Heart failure “should have been No. 1 on the list of possible causes” for Watkins’ symptoms, said Ronald Wyatt, chief science and chief medical officer at the Society to Improve Diagnosis in Medicine, a nonprofit research and advocacy group.

Pregnancy-related deaths among Black mothers has increased dramatically in recent years. The United States has the highest maternal mortality rate among developed countries. According to the Centers for Disease Control and Prevention, non-Hispanic Black mothers are 2.6 times as likely to die as non-Hispanic White moms. More than half of these deaths take place within a year after delivery.

Research shows that Black women with childbirth-related heart failure are typically diagnosed later than White women, said Jennifer Lewey, co-director of the pregnancy and heart disease program at Penn Medicine. That can allow patients to further deteriorate, making Black women less likely to fully recover and more likely to suffer from weakened hearts for the rest of their lives.

Watkins said the diagnosis changed her life. Doctors advised her “not to have another baby, or I might need a heart transplant,” she said. Being deprived of the chance to have another child, she said, “was devastating.”

Racial and gender disparities are widespread.

Women and people of color suffering from heart attacks are more likely than others to be discharged without diagnosis or treatment.

Black people with depression are more likely than others to be misdiagnosed with schizophrenia.

People of color are less likely than Whites to be diagnosed early with dementia, depriving them of the opportunities to receive treatments that work best in the early stages of the disease.

Misdiagnosis isn’t new. Doctors have used autopsy studies to estimate the percentage of patients who died with undiagnosed diseases for more than a century. Although those studies show some improvement over time, life-threatening mistakes remain all too common, despite an array of sophisticated diagnostic tools, said Hardeep Singh, a professor at Baylor College of Medicine who studies ways to improve diagnosis.

“The vast majority of diagnoses can be made by getting to know the patient’s story really well, asking follow-up questions, examining the patient, and ordering basic tests,” said Singh, who is also a researcher at Houston’s Michael E. DeBakey VA Medical Center. When talking to people who’ve been misdiagnosed, “one of the things we hear over and over is, ‘The doctor didn’t listen to me.’”

Racial disparities in misdiagnosis are sometimes explained by noting that minority patients are less likely to be insured than White patients and often lack access to high-quality hospitals. But the picture is more complicated, said Monika Goyal, an emergency physician at Children’s National Hospital in Washington, D.C., who has documented racial bias in children’s health care.

In a 2020 study, Goyal and her colleagues found that Black kids with appendicitis were less likely than their White peers to be correctly diagnosed, even when both groups of patients visited the same hospital.

Although few doctors deliberately discriminate against women or people of color, Goyal said, many are biased without realizing it.

“Racial bias is baked into our culture,” Goyal said. “It’s important for all of us to start recognizing that.”

Demanding schedules, which prevent doctors from spending as much time with patients as they’d like, can contribute to diagnostic errors, said Karen Lutfey Spencer, a professor of health and behavioral sciences at the University of Colorado-Denver. “Doctors are more likely to make biased decisions when they are busy and overworked,” Spencer said. “There are some really smart, well-intentioned providers who are getting chewed up in a system that’s very unforgiving.”

Doctors make better treatment decisions when they’re more confident of a diagnosis, Spencer said.

In an experiment, researchers asked doctors to view videos of actors pretending to be patients with heart disease or depression, make a diagnosis, and recommend follow-up actions. Doctors felt far more certain diagnosing White men than Black patients or younger women.

“If they were less certain, they were less likely to take action, such as ordering tests,” Spencer said. “If they were less certain, they might just wait to prescribe treatment.”

It’s easy to see why doctors are more confident when diagnosing White men, Spencer said. For more than a century, medical textbooks have illustrated diseases with stereotypical images of White men. Only 4.5 percent of images in general medical textbooks feature patients with dark skin.

That may help explain why patients with darker complexions are less likely to receive a timely diagnosis with conditions that affect the skin, from cancer to Lyme disease, which causes a red or pink rash in the earliest stage of infection. Black patients with Lyme disease are more likely to be diagnosed with more advanced disease, which can cause arthritis and damage the heart. Black people with melanoma are about three times as likely as Whites to die within five years.

The COVID-19 pandemic helped raise awareness that pulse oximeters — the fingertip devices used to measure a patient’s pulse and oxygen levels — are less accurate for people with dark skin. The devices work by shining light through the skin; their failures have delayed critical care for many Black patients.

Seven years after her misdiagnosis, Watkins is an assistant professor of social work at North Carolina Central University in Durham, where she studies the psychosocial effects experienced by Black mothers who survive severe childbirth complications.

“Sharing my story is part of my healing,” said Watkins, who speaks to medical groups to help doctors improve their care. “It has helped me reclaim power in my life, just to be able to help others.”