The commonest single cause of maternal death is from post-partum haemorrhage, from which one woman dies every 7 minutes.
Health Technologies to Save Mothers. PATH.org video.
References:
Maternal mortality: one death every 7 min. The Lancet, Volume 375, Issue 9728, Pages 1762 - 1763, 22 May 2010.
Maternal mortality: one death every 7 min. The Lancet, Volume 375, Issue 9728, Pages 1762 - 1763, 22 May 2010.