Having Sons Reduce Lifespan of Mothers: Study

A latest Finnish study claims that women who give birth to sons have a slightly shorter life span than women who give birth to girls.

According to a study conducted by researchers at the University of Turku, Finland, the risk of death increased by 7 percent per year for each son a woman gave birth to. The study took into consideration the socio-economic status of the women.

To go about with the finding, study lead Dr. Samuli Helle of the University of Turku worked on data that had the post-reproductive survival records of more than 11,000 mothers in pre-industrial Finland, using records kept by the Lutheran Church. The data involved was taken from eight Finnish parishes in the 17^th to 20^th centuries living in an agricultural society with no access to either medical care or modern birth control.

"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," Helle was quoted as saying in the journal Nature. "I'm not surprised the results have been mixed, because the previous studies have involved different societies, cultural practices and so on."

On examining the data, the researchers noticed that most women in the community gave birth to their last kids at the age of 37 years. Based on the sex of the children, the life expectancy would vary. If the woman had no sons, she would live for another 33.1 years. With three sons, she would live for 32.7 years, and with six sons, she would live for 32.4 years.

Therefore, more number of sons a woman gives birth to, lower the post-reproductive survival is.

The researchers state that giving birth to sons reduces the life span of the mothers because giving birth to sons raises the levels of testosterone in their mothers which weakens the immune system. Details according to the journal Nature suggest that boys grow faster in a mother's womb when compared to girls. They are heavy to carry, causing strain for the women. A study conducted earlier suggests that women burn up excess of their energy in producing breast milk for boys.

The study found that father's life expectancy did not depend on the gender of the children.

"The relative importance of biological versus cultural factors remains an open question," Helle was quoted as saying in Nature. "We need more data, such as how many sons versus daughters helped in everyday tasks, what age they actually started to work outside the home and so on."

The study was published in the Royal society journal Biology Letters.