The U.S. maternal mortality rate in 2018 was 17.4 maternal deaths per 100,000 live births, or 658 total deaths, according to a CDC report published Thursday—marking the first new data on maternal mortality rates that the agency's released in over a decade.

How the US maternal mortality crisis is rooted in inequality (and 4 ways to combat it)

CDC pauses reports on maternal mortality for 10+ years

The federal government in 2003 added a checkbox to standard death certificates intended to help the government track maternal mortality rates. The change allowed medical professionals to indicate on death certificates whether the deceased person was pregnant or had given birth around their time of death.

However, CDC paused on releasing reports on U.S. maternal mortality rates over concerns the data collected was incomplete and potentially incorrect.

For instance, the federal government didn't require states to use this checkbox, and some states "were slow to adopt the change," Vox reports. Further, Donna Hoyert, a health scientist in the mortality statistics branch of the National Center for Health Statistics (NCHS), said, "[T]he checkbox was sometimes checked in error."

But as of 2017, all 50 states included some type of checkbox on death certificates allowing officials to track maternal mortality. Armed with more complete data, CDC researchers set out to draft a new report on maternal mortality and adjusted methodology intended to minimize errors. To do so, the researchers analyzed checkbox data on individuals ages 10 to 44. The researchers only looked at checkbox data for individuals ages 44 to 54 in cases where supporting cause-of-death information was available. The report included maternal-related deaths that occurred while a person was pregnant, as well as up to 42 days after delivery.

Hoyert said the change is intended "to minimize the role of the checkbox without supporting cause-of-death information where research has found the checkbox to be less reliable."

Elliott Main, a professor of obstetrics and gynecology at Stanford University School of Medicine and medical director of the California Maternal Quality Care Collaborative, explained, "[W]hat NCHS has done is to say, 'OK we're not going to include any pregnancies over the age of 45 if the only reason we would be considering it is the pregnancy checkbox.' … Meaning that there was nothing in the cause of death or the other descriptions on the death certificate that even mentioned pregnancy." He said, "That's a good start."

Findings

The researchers found that the overall maternal mortality rate was 17.4 deaths per 100,000 live births in 2018, and that the maternal mortality rate increased with age. According to the report, women over the age of 40 died at a rate of 81.9 per 100,000 births, making them more than seven times as likely to die from maternal-related causes than women under age 25:

The researchers also found that the maternal death rate for black women was more than double the rate among white women, with black women dying at a rate of 37.1 deaths per 100,000 live births, compared with a rate of 14.7 deaths per 100,000 live births among white women:

Data shows US lags behind other countries, experts say

Experts said the data shows the United States lags behind other countries when it comes to maternal health.

Eugene Declercq, a professor of community health sciences at Boston University School of Public Health, said if you look at the World Health Organization's most recent maternal mortality rankings and compare other countries' rates with the U.S. rate from the new CDC report, the United States would rank 55th when it comes to maternal mortality. Even worse, "If you limit the comparison to … similarly wealthy countries, … the U.S. would rank 10th—out of 10 countries," Declercq said.

And experts said the latest CDC report still might underestimate the U.S. maternal mortality rate.

Main cautioned that "it can be a bit tricky to determine whether a woman was pregnant or that the death was related to the pregnancy." That measurement becomes even harder "when you're looking at causes that are not directly tied to the pregnancy, like blood clots or cardiovascular disease in particular, heart attacks, cardiomyopathy, and related complications," he said.

Still, Janine Clayton, director of the Office of Research on Women's Health at NIH, said the new report "represent[s] a landmark" in research on maternal mortality in the United States. "It gives us more evidence and more confidence that these maternal mortality rates that we're seeing in the United States—that are still higher than those of our peer countries—truly represent a critical public health issue and serious concern for the health of women," she said.

Clayton said more research is needed to understand why the racial gap in maternal mortality rates persists and to figure out ways "to address factors that increase risk of mortality."

Bob Anderson, chief of NCHS' mortality statistics branch, said maternal mortality "is an important indicator of the health of a nation." He added, "These are deaths that are almost entirely preventable, and these are deaths that are occurring at a time that is supposed to be about birth, not death, so it's particularly poignant when a mother dies in childbirth."

Shah said the new report could help efforts to address maternal mortality. "It is hard to fix something you can't see," Shah said. "Even with more conservative estimates, the topline findings verify the concerns of the scientific and medical community. There are hundreds of preventable pregnancy-related deaths each year. The rate appears to be rising, and there are stark racial inequities in outcomes" (Belluz, Vox, 1/30; Howard, CNN, 1/30; Chuck, NBC News, 1/30).