Do you have a source for that? Looks like homicide remains the leading cause of death of women during the perinatal period, and in general the greatest risk a pregnant woman faces is her partner.
http://www.ncbi.nlm.nih.gov/pubmed/22015873
http://www.webmd.com/baby/news/20010320/number-1-cause-of-de...
But even in the US suicide is a leading cause of death of women in the perinatal period.
Here's cites for the UK:
http://bjp.rcpsych.org/content/183/4/279
And the WHO lists suicide as a leading cause of death in the Western world, and in the two most populous countries
> Suicide is a leading cause of maternal death in developed countries. The 1997-1999 Report of the Confidential Enquiries into Maternal Deaths in the UK identified psychiatric disorders, and suicide in particular, as the leading cause of maternal death (6). Suicide is now a leading cause of death in young women in the reproductive age group in the world's two most populous countries, India and China