New research has refuted what Science magazine reported five years ago and what has been cited time and again, and not always properly. Good news for all mothers: There is not the least evidence that giving birth to a son as compared to a daughter ever has shortened or ever will shorten the life of a woman.
Back in May 2002, Helle and co-workers have analyzed population register data of pre-industrial Sweden and found that giving birth to sons shortened the life of women. They were even ready to explain this correlation: Sons, in their opinion, are a greater physiologic burden than daughters, and the testosterone produced by the male fetuses may have a negative impact on the hormone balance of the women.
Despite the fact that this analysis has been restricted to a pre-industrial population, the finding has been spread by popular media as relevant for women of today: "Those sons really will be the death of you, mom" has shown up at position 20 of a Google search today.
More data unmask a bias
Recently, Cesarini and co-workers have re-analyzed the Swedish data and published their new findings on maternal longevity and the sex of offspring in pre-industrial Sweden. Extending the original database of Helle and others by considerably more data from the same region and time period, they no longer found any evidence of a negative impact of sons. It seems that the smaller database of Helle has been affected by some variable bias that has not been filtered out properly.
Photo credit: flickr.com/photos/maistora/370381796/