In 2003, UC Berkeley researchers Gordon Dahl and Enrico Moretti analyzed U.S. Census data from over three million adults and found that couples with a female first-born were five percent more likely to divorce than those couples with a first-born boy. The number jumped to 10 percent for couples that had as many as three daughters.
The reasoning behind why this was a trend ranged from economic reasons (that boys are better for families and finances) to the belief that daughters "inspire" their mothers to leave bad relationships because of the built-in emotional support.
But that's just not true, according to new research from Duke University. Duke economist Amar Hamoudi and Jenna Nobles, a University of Wisconsin-Madison sociologist, suggest that girls may be "hardier" than boys — even in the womb — and better able to survive a pregnancy with a mother in the midst of a troubled marriage.
The reason? Girl power! Scientific evidence suggests that a female's survival advantage starts in the womb — and those strong embryos are able to withstand the stress of pregnancy, according to the study.
"Many have suggested that girls have a negative effect on the stability of their parents' union," Hamoudi writes in the study, published in the journal Demography. "We are saying: 'Not so fast.'"
Hamoudi and Nobles analyzed longitudinal data from a sample of U.S. residents between 1979 and 2010. The data showed that women who reported more relationship strife that eventually caused divorce were more likely to give birth to girls.
"Girls may well be surviving stressful pregnancies that boys can't survive," Hamoudi said. "Thus girls are more likely than boys to be born into marriages that were already strained."
Women with more marital problems were more likely to give birth to more girls in the future, too.
The pair believes that family dynamics affect children even before birth — so even though your child isn't born yet, she's being affected by how you interact with your partner and family.
"It's time for population studies to shine a light on the period of pregnancy," Hamoudi said. "The clock does not start at birth."
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