(CNN) — The mortality rate of pregnant and recently pregnant women in the United States rose almost 30 percent between 2019 and 2020, according to a new study.

The study, published Friday in JAMA Network Open, analyzed information on 4,535 deaths collected by the US Centers for Disease Control and Prevention's National Center for Health Statistics from 2019 to 2020. The researchers looked at deaths in women who were pregnant or were within a year of giving birth.

The women's mortality rate from any cause increased from 54 deaths per 100,000 live births in 2019 to 70 in 2020, the researchers found. Mortality rates increased 22 percent for pregnancy-related causes and 36 percent for nonpregnancy causes.

Causes not related to pregnancy accounted for more than half of the women's deaths in 2020, the researchers say. Accidental drug poisoning was the most common, followed by motor vehicle collisions and homicide, with mortality rates of 12.2 percent, 5.9 percent and 5.5 percent, respectively. The mortality rate involving suicide did not significantly change.

The study authors also identified significant racial and ethnic disparities. Mortality rates were three to five times higher among American Indian or Alaska Native women for every cause except suicide. Black women had similarly high mortality rates across all causes, with 5.3 times higher risk of dying from homicide.

"One of the main messages, I think, from this is really that there's a much bigger societal problem facing pregnant women and new mothers who are in that postpartum period where, you know, that's a very stressful time of life. What this points to is that there's particular vulnerability in this population to some of these other social factors," said Jeffrey Howard, an author of the study and associate professor of public health at the University of Texas at San Antonio.

He says the research is consistent with increasing death rates among pregnant and postpartum women, but says this trend was exacerbated by the Covid-19 pandemic. The pregnancy-related mortality rate increased by 4.4 percent annually from 2015 to 2019 compared with 29 percent from 2019 to 2020.

What Howard finds especially striking is the number of deaths not due to pregnancy.

"If you go back to 2015, most of the deaths in this population were from pregnancy-specific causes. I think it was around 60 percent and 40 percent were from other causes. By 2020, it's kind of flip-flopped where the majority of the deaths are coming from other causes, not pregnancy-specific," Howard said.

The findings can be largely attributed to the stressors brought on by the pandemic, he said. Rebecca Lawn, an epidemiologist at the Harvard T.H. Chan School of Public Health, agrees.

The findings "really just highlight and bring into discussion factors that you don't traditionally think of with mortality of pregnant women," said Lawn, who was not involved with the research. "And I think it's the same with the pandemic. The measures that were put in place to keep people safe from Covid-19, such as stay-at-home orders, actually can exacerbate women's experiences of intimate partner violence."

Lawn says pregnancy is a time when intimate partner violence often begins or increases in severity. Along with access to firearms, it's one of the highest risk factors for women being murdered during or after pregnancy, she said.

"But [pregnancy] also comes at a time where, if women have access to health care, there is then a time for more opportunities to help and protect women in terms of screening for intimate partner violence or educating on intimate partner violence. So I think that access to care is a really important component."

Experts say that addressing substance use during and after pregnancy is also critical as death from opioid overdose among pregnant and postpartum women has increased in recent years, mirroring trends in the general population.

"We have a duty as a society to acknowledge that it is OK to not be OK and destigmatize mental health so that individuals feel comfortable to seek help," said Dr. Veronica Gillispie-Bell, an OBGYN at Ochsner Medical Center in New Orleans. "We should also be trained on using [the opioid overdose treatment] Narcan and understand how to access it, and we have to address community violence."

As for racial and ethnic disparities, experts say these findings are consistent with research showing that Native American and Black women are at significantly higher risks of pregnancy-related death and that structural issues must be addressed.

"We've seen study after study show how discrimination and structural racism are at play at multiple levels within our health care system as well as communities at large, preventing women from accessing quality care that is respectful," said Dr. Kamila Alexander, an associate professor at the Johns Hopkins School of Nursing.

Research has shown that more than four out of five pregnancy-related deaths are preventable, but experts say systemic changes are necessary.

"The year after birth is a critical time period. Women are still at risk for a number of pregnancy-associated causes of death; however, for the most part, they are disconnected from the health care system. It is important for community and family to provide support and understand the issues that are facing postpartum women put them at risk for death," Gillispie-Bell said.

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