There is a pretty interesting document on maternal mortality in the United States, with the link below (prepared by the U.S. Department of Health and Human Services):
What stands out (for me) is that in the United States in 1935, maternal mortality averaged across all races was just under 600 deaths for every 100,000 live births. In 2007, the average was 12.7.
The data that I am seeing shows that in 1991, the death rate hit its bottom - about 4 maternal deaths for every 100,000 live births. In 2006, it was about 9. According to the report, the reasons for the increase were the following:
In a state-level ecological analysis, higher levels of poverty rates, percentage of immigrant population, and cesarean rates were independently associated with higher maternal mortality rates.According to the report, the poverty rate had the highest correlation with increased maternal mortality rates. I think that tends to make sense because if you are at or below the poverty line, you probably have no health insurance, and are less likely to be able to consult with an ob/gyn about the progress of the pregnancy, and possible complications.