As noted by, for example, a report last year from ProPublica and National Public Radio, the United States has by far the highest death rate in the developed world for women around the time of giving birth. It's not even close: As of 2015, there were 26.4 maternal deaths per 100,000 live births in the U.S. while in other advanced countries the rate ranged from 3.8 to 9.4. (These figures are from the NPR/ProPublica report; other estimates differ somewhat because of varying definitions and methods of measurement, but they're similar.)
Even worse, that rate has been rising in the U.S. even as it declines elsewhere. Here's a graph from the article on the NPR website:
For possible reasons why, see this article by Dr Felicia Lester, MD, medical director of gynecologic services at the University of California, San Francisco.
Bad as the overall rate is, maternal mortality among African American mothers is about three times worse. Here's a summary of the situation and its likely causes from Dr Aaron Carroll, whose YouTube videos I often share here: