There are many reasons why this is happening. Here I list only a few:
1) The overuse of c-sections. Even in a scheduled routine c-section, the mother is twice as likely to die than if she had a vaginal birth.
2) Poor health care for poor people. Women living in poverty are far more likely to die from complications in childbirth than rich women.
3) Poorly staffed medical facilities and poor communication among staff. Many times when a woman dies in childbirth it is because the signs that something was wrong were not noticed or not reported until it was too late. I know medical personnel are only human and they take their jobs very seriously, but they need the support and the tools to do their job better.
For more information: Amnesty International Report