Study says U.S. maternal death rate crisis is really case of bad data

A new study calls into question the extent of the maternal mortality crisis in the United States, which has long posted a disproportionately high rate of maternal deaths compared with peer nations.

Data classification errors have inflated U.S. maternal death rates for two decades, according to the study published Wednesday in the American Journal of Obstetrics & Gynecology. Instead of the maternal death rate more than doubling since 2002, it has remained flat, researchers found.

Maternal mortality has been called a leading public health concern in Indiana, with the state regularly ranking among those with the highest rates.

“There has been a lot of alarm and apprehension surrounding the fact that some of these reports show a threefold increase in maternal mortality, and that is not what we found. We found low and stable rates,” said K.S. Joseph, the study’s lead author and professor in the departments of obstetrics and gynecology and the School of Population and Public Health at the University of British Columbia in Vancouver.

A change in the way pregnancy was noted on death certificates 21 years ago to improve the detection of maternal deaths led to “substantial misclassification” and an “overestimation of maternal mortality,” the study found.

In 2003, the National Vital Statistics System added a checkbox to death certificates to note whether the deceased person was pregnant or had recently been pregnant to address concerns that pregnancy-related deaths were being undercounted.

But the box was checked for many deaths that were unrelated to pregnancy or childbirth, researchers found. For example, hundreds of deaths of people ages 70 or older were mistakenly classified as having been pregnant. Deaths from cancer and other causes were also counted as maternal deaths if the box was checked. As a result, the maternal mortality rates dramatically increased since 2003.

Researchers noted that gaping racial disparities remain, especially between White and Black pregnant people. Black pregnant people die at nearly three times the rate of their White peers because they face higher rates of pregnancy complications such as ectopic pregnancy and eclampsia, as well as chronic diseases such as high blood pressure, heart disease and kidney failure, researchers found.

Some experts say the study’s biggest takeaway is the persistent racial disparities, with many pregnant Black people experiencing more medical complications involving Caesarean sections, postpartum hemorrhaging and preterm births. However the data is calculated, the pattern remains the same, said Colleen Denny, an associate professor in the department of obstetrics and gynecology and director of family planning at NYU Langone Hospital as well as a fellow of the American College of Obstetricians and Gynecologists.

“We should be targeting a lot of our public outreach to focus on conditions that are affecting patients of color while they’re pregnant,” said Denny, who was not involved with the study.

Joseph, whose 2017 paper previously noted the inflated U.S. maternal mortality rates, said: “Many maternal deaths, perhaps more than a half of maternal deaths, are preventable, so we have to initiate programs that address these specific causes of death and prevent them.”

The impetus for the new study was researchers’ confusion over why the U.S. maternal mortality rate was so high compared with other high-income nations, said Cande Ananth, a senior author of the study and chief of epidemiology and biostatistics at Rutgers Robert Wood Johnson Medical School. The authors said U.S. maternal mortality is actually comparable to that of Canada and Britain. Even with the adjusted rate, however, the U.S. rate would remain higher than most peer nations.

The authors decided to ignore the checkbox and count only deaths that listed a cause related to pregnancy.

Under the new criteria, researchers found that the mortality rates were 10.2 per 100,000 live births from 1999 to 2002 and 10.4 from 2018 to 2021. In contrast, the National Vital Statistics System method produced a mortality rate of 9.65 from 1999 to 2002 and 23.6 from 2018 to 2021.

An agency spokesman declined to comment on the new study and instead pointed to its own 2018 report.

In that report, the National Vital Statistics System reviewed several studies that found the pregnancy-and-birth checkbox was being used in error, particularly for people ages 45 and older. At that time, the agency’s report said that without the checkbox, the rate for maternal mortality would have remained flat since 2002.

To correct for misuse of the checkbox, the agency changed the way it counted deaths. It stopped classifying deaths as pregnancy-related for people over age 44 unless there was a specific cause of death tied to pregnancy or delivery. But for those 44 or younger, the agency continued to classify every death with the box checked as being related to pregnancy or delivery, even if the specific cause of death was unrelated.

Despite the study’s conclusion that use of the checkbox led to excessively high calculations of maternal mortality, the National Vital Statistics System said in its 2018 report that it would continue to calculate rates from the checkbox to avoid undercounting maternal mortality.

Other experts say the new study can be helpful to expand the ways public health initiatives are targeted to yield better outcomes.

This is an opportunity to rethink how the nation tracks maternal health outcomes and create a better system to help identify problems and interventions, said Chiamaka Onwuzurike, medical director of the gynecology clinic at Brigham and Women’s Hospital and an instructor at Harvard Medical School who was not involved with the study. “If we keep our blinders up and think that things are working well and our systems are tracking things appropriately, what good does that really do us?”

In 2022, the White House released a blueprint to address the maternal health crisis, outlining federal actions and long-term goals for improvement. But the federal government needs to better track progress toward achieving these goals, according to a February report from the Government Accountability Office.

Examining indirect causes of maternal deaths, including mental health, can lead to policies and interventions aimed at minimizing the instances of non-obstetric causes of death, according to Amita Vyas, a professor in the department of prevention and community health and director of George Washington University’s Center of Excellence in Maternal and Child Health.

“When we think about maternal deaths, it’s not just in pregnancy or during childbirth,” Vyas said. “We lose the ability to design lifesaving interventions if we disregard other indirect pregnancy-related factors in the postpartum period.”