A new report highlights concerns about the care mothers-to-be get in US hospitals.

Most of the pregnancy-related deaths that occur in the United States are preventable, the CDC said in a report released Tuesday.

The report notes that about 700 women die each year in the US due to complications related to pregnancy or childbirth. More than half of them die from preventable causes, and this issue disproportionately affects minority women.

CDC researchers studied pregnancy-related mortality ratios (PRMRs) for the new report. A PRMR is the number of pregnancy-related deaths that occur for every 100,000 live births. These deaths can occur not only during pregnancy itself but also during childbirth or up to one year after a baby is born.

Overall, the national PRMR for the years 2011 through 2015 was 17.2 maternal deaths for every 100,000 live births. But the PRMRs for black women and American Indian/Alaska Native were 3.3 and 2.5 times higher, respectively, than the PRMR for white women. For every 100,000 African American women who gave birth to a living baby, about 43 died. For American Indian/Alaska Native women, PRMR was about 33, while for white women it was only 13. “Significant racial/ethnic disparities in pregnancy-related mortality exist,” the authors wrote.

Among the maternal deaths for which time of death was known, about 31% occurred while the mother was pregnant, and about 17% occurred the day the baby was delivered. About 19% occurred between one and six days after the mother gave birth, while about 21% occured between one week and 42 days postpartum. Just under 12% occured between 42 days and one year after giving birth.

Leading causes of pregnancy-related deaths during this time period included cardiovascular conditions, bleeding, and infections. About 60% of maternal deaths studied for the report were preventable—a fact that did not differ among racial and ethnic groups, the authors noted.

The report says there is not a single quick fix to this highly complex problem. The fact that pregnant women and new mothers are dying from preventable causes raises concerns about the quality of care they get in US hospitals (as well as after they’re sent home), the authors wrote—especially African American and American Indian/Alaska Native women.

“These data demonstrate the need to address the multiple factors that contribute to pregnancy-related deaths during pregnancy, labor and delivery, and postpartum,” the authors wrote. “Reducing pregnancy-related deaths requires reviewing and learning from each death, improving women’s health, and reducing social inequities across the life span, as well as ensuring quality care for pregnant and postpartum women.”

A number of strategies could be put in place to improve the maternal death rate in the United States, the new report says. “In the postpartum period, follow-up care is critical for all women, particularly those with chronic medical conditions and complications of pregnancy,” the authors wrote. (They mention hypertensive disorders, such as preeclampsia, as one specific example.) They also recommend that women who are at high-risk for complications be given access to facilities that can provide the specialized care they need.