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Study Questions 'Rising' Level of U.S. Maternal Deaths
  • Posted March 13, 2024

Study Questions 'Rising' Level of U.S. Maternal Deaths

For years, U.S. health officials have been sounding the alarm over a steady rise in pregnancy-related deaths among American women, with numbers that appeared to far outstrip those of other wealthy nations.

However, the statistics behind those trends could be flawed, researchers report in a new study.

Their detailed reanalysis of government data from 2002 through 2021 found that -- while still comparatively high -- maternal mortality rates in the United States are lower than prior estimates and have actually held steady over time.

The problem seems to lie in standardized death certificates that include a "pregnancy checkbox," indicating whether or not the deceased was pregnant at the time of death, the researchers explained.

Too often, a ticked pregnancy checkbox alone was taken as evidence that something about the pregnancy caused the woman's death.

In many cases, the pregnancy had nothing to do with the fact that the woman passed away from cancer or a car accident, or any number of other causes.

Maternal deaths are defined as deaths that occur during pregnancy, childbirth or shortly thereafter from conditions directly related to or exacerbated by pregnancy or birth.

So, “if you're pregnant and die in a car crash, that's not a maternal death,” said senior study author Cande Ananth, an epidemiologist researcher at Rutgers University in New Brunswick, N.J.

“A big change driving recent increases in the official numbers stems from the tendency to include more and more cancers unrelated to pregnancy in maternal death rates," he explained in a Rutgers news release. "A woman who had a diagnosis of breast cancer before conception and then died after the pregnancy ended, or a woman who would have died if she'd never gotten pregnant, will be counted as a maternal death.”

Over time, errors like these were added into calculations of maternal mortality compiled by the National Vital Statistics System (NVSS), part of the U.S. Centers for Disease Control and Prevention. The agency has issued statements suggesting that U.S. maternal mortality rates have more than tripled over the past 20 years, to reach nearly 33 maternal deaths per 100,000 live births in 2021. That's a rate that's much higher than any other wealthy nation.

However, when Ananth's team took a closer look at deaths that were clearly due (at least in part) to pregnancy-related factors, the recent U.S. maternal death rate fell to about 10 deaths per 100,000 live births.

That's a number that's held steady over the past few years and, while still high, is closer to rates seen in other high-income nations.

Recognized errors

Ananth's group said there have long been red flags that relying solely on the pregnancy checkbox on death certificates had its flaws.

For example, he said that for years the NVSS counted a person among "maternal mortality" statistics if the pregnancy checkbox was checked -- even if elsewhere on the form it listed the woman as elderly, and even if (in some cases) the deceased was listed as male.

By 2017, the CDC had recognized that these types of errors were occurring, and restricted the use of the pregnancy checkbox to only deceased women between the ages 15 and 44.

The agency also stopped reporting maternal mortality rates for the years 2007 through 2017, based on an acknowledgement of those errors, Anand's group noted.

However, the pregnancy checkbox still helped inflate numbers going forward, the researchers discovered. That's because relying on the checkbox fails to differentiate between deaths that occurred because of a pregnancy and deaths that occurred during a pregnancy.

“The CDC has acknowledged in the past that errors were artificially inflating numbers, but their efforts to correct those errors haven't worked,” said Ananth, chief of epidemiology and biostatistics in the Department of Obstetrics, Gynecology, and Reproductive Sciences at Rutgers.

His team noted that in many ways, the care of American women during a pregnancy has actually improved over time. Their analysis found significant declines in maternal deaths linked to infection, hypertensive disorders in pregnancy such as preeclampsia or eclampsia and other treatable causes.

However, at the same time, American women have become increasingly unhealthy when they enter a pregnancy. According to the researchers, that probably explains why maternal death rates have remained steady, despite improvements in care.

Ananth and his colleagues were joined in the research by scientists from the University of British Columbia in Canada and elsewhere. They published the findings March 12 in the American Journal of Obstetrics and Gynecology.

Still no reason to relax

Reviewing the findings, Robert Anderson, chief of mortality statistics for the CDC, said the agency stands by its more recent calculations.

“We feel fairly confident that there has been an increase [in maternal mortality], particularly during the pandemic,” Anderson told CNN. “We went from underestimating to overestimating, so we had to make that correction. But I feel fairly confident that the increases since 2018 are real.”

Dr. Elliot Main is a professor of obstetrics and gynecology at Stanford University School of Medicine and the former medical director of the California Maternal Quality Care Collaborative. He wasn't involved in the new study, but he agreed with the researchers that the CDC's methodology was too simplistic.

"The pregnancy checkbox shouldn't be taken as proof of a pregnancy, but the case needs to be looked at further before it's added to the total,” he told CNN.

"It is easy to identify direct maternal deaths -- like the deaths from hemorrhage and hypertension, and the deaths from blood clots, those are clearly related to pregnancy," he said. "But there's considerable variation around including causes not directly related to the pregnancy, the so-called indirect causes of maternal death, such as cancers, heart disease or overdoses.”

Main stressed that the United States still has a ways to go before its maternal mortality rates decline to that of other affluent nations. Adjusting the numbers based on the new analysis shows that the United States still has a relatively high maternal death rate, he said -- it's "just not as terrible" as folks once thought.

The March of Dimes, which focuses on the health of mothers and infants, agreed this is no time to relax when it comes to maternal deaths.

“Many of the deaths that are detected through the checkboxes are correct,” Dr. Emre Seli, chief scientific adviser for the organization, told CNN. He added that statistics clearly show that Black women remain at a higher risk of dying from pregnancy-related causes than white women.

“We agree that we should invest into researchers doing better surveillance of maternal deaths,” he said. “But the undisputable conclusions of this publication would be that we're not doing any better in the maternal death scenario today compared to 20 years ago, and there are immense health inequities in the matter.”

More information

Find out more about maternal deaths at the March of Dimes.

SOURCES: Rutgers University, news release, March 12, 2024; CNN

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