The gender of a baby can predict a mother's life expectancy. Elaborating on this point, a new study states that giving birth to sons can have a negative impact on a woman's life span.
The findings, reported in the journal Biology Letters, come from a team of researchers from the University of Turku in Finland. Study lead author Samuli Helle and colleagues compared the life span of mothers who gave birth to boys and those who gave birth to girls.
They found that having more boys shortens a mother's life as compared to giving birth to girls. For the study, researchers analyzed Finnish villagers in pre-Industrial Scandinavia. The data provided details on more than 11,100 women and 6,300 men, born in the 17th and 20th centuries. Researchers found a mother's risks of dying going up 7 percent higher each year with every additional son she has.
The current study was based on a previous study reported in the journal Science, conducted by the researchers earlier, which found that with each son, a mother's life reduced by 34 weeks.
Both biological and cultural factors could possibly be playing important roles in this occurrence, and daughters helping mothers in everyday household work may be a factor that lengthens a mother's life expectancy, researchers said.
"The relative importance of biological versus cultural factors remains an open question," Helle told 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."
Health experts and previous studies put forward some other explanations for this occurrence. According to one explanation, boys are normally heavier than girls and they put physical stress on a pregnant woman's body.
And since boys are born normally heavier than girls and make mothers spend more energy to produce breast milk. A third explanation is that while bearing a son, a woman's testosterone level goes up, negatively affecting her immune system.
