Media playback is unsupported on your device Media caption Why does the US lead the developed world in maternal mortalities?

Pregnancy-related deaths are rising in the US and the main risk factor is being black, according to a new study from the Centers for Disease Control.

The study found that rates of maternal mortality are about three times higher among black, Native American and Alaska Native women than white women.

Approximately 700 American women die every year from pregnancy-related complications.

The study found that most of these deaths - about 60% - were preventable.

"The bottom line is that too many women are dying largely preventable deaths associated with their pregnancies," said Anne Schuchat, Centers for Disease Control's (CDC) principal deputy director during a call with US media.

"We have the means to identify and close gaps in the care they receive."

The American College of Obstetricians and Gynecologists, which was not involved in this report, released a statement last week that also acknowledged the racial prejudice within the healthcare system

"The leading factor" in maternal mortality is race, the statement said. "This disparity is due, in part, to racial bias and overt racism that exists in the provision of health care and in health system processes."

Image copyright Getty Images Image caption A new study from the CDC finds huge racial disparity in maternal mortality

The CDC study looked at maternal mortality from 2011 to 2017. There were more than 3,400 pregnancy-related deaths over this five-year period in the US.

Among white women, 13 mothers died for every 100,000 live births. For black women, this number more than tripled, with more than 42 mothers dying for every 100,000 live births.

Among Native American and Alaska Native women this number was 32.5, and among Asian and Pacific Islander women it was 14.2.

The lowest rate was among Hispanic women: just over 11 mothers died for every 100,000 live births.

A primary cause of pregnancy-related deaths was cardiovascular disease. Heart disease and strokes caused more than a third of pregnancy-related deaths, according to the CDC.

The rise in maternal mortality in the US is out of step with the rest of the world. Globally, maternal mortality dropped about 44% between 1990 and 2015, according to the World Health Organization.