Researchers at University of Turku, Finland, found that sons often required more energy from the mothers when they were small though the risk on their health reduced as the children grew up. The researchers analyzed data from a pre-industrial village in Finland during the seventeenth to mid-twentieth centuries and found that a woman's lifespan reduced by seven percent per year every time she gave birth to a son.
This effect was more prominent in large families and among families whose access to food and health care are poor.
"Previous investigations into the effect of the gender of a baby on its mother's lifespan have been mixed, so our new analysis really is just another brick in the wall. I'm not surprised the results have been mixed, because the previous studies have involved different societies, cultural practices and so on", lead researcher Samuli Helle said.