STOCKHOLM, Sweden, Sept. 25 (UPI) -- Moms who gain weight from the beginning of a first pregnancy to the beginning of a second may be more likely to have a boy, a U.S. and Swedish study found.
Researchers at the Harvard School of Public Health in Boston and Karolinska Institutet in Stockholm, Sweden, examined the Swedish Birth Registry, which included 220,889 women who had successive pregnancies between 1992 and 2004.
The study, published in the journal Fertility & Sterility, found a male to female sex ratio of the second pregnancy increased linearly with the amount of weight change from the first to second pregnancy, from 1.024 in women who lost more than 1 unit body mass index to 1.080 in women who gained 3 or more units.
Villamor noted that women should not gain weight to try to influence the sex of their baby.
"Weight gain before pregnancy carries significant risks to the mother and the baby, and should not be practiced to influence the odds of having a boy," Villamor said in a statement. "Other factors of which weight gain is only an indicator could be at play here."
