Over the last few centuries, women in Finland who had many sons tended to have a shorter life span after last giving birth than women who had daughters.
Having many sons may shorten women's lives after their last birth more than having daughters, according to new research.
The findings, which came from a group of Finnish women born mostly before industrialization, are correlational, so they can't prove sons actually cause shorter lives for their moms relative to daughters. And because the effect varies across the world, social factors, rather than intrinsic biological effects, may be to blame.
For the rest of the story: http://www.livescience.com/27466-sons-may-shorten-mothers-lives.html