The researchers found that daughters of obese mothers, versus normal- or under-weight mothers, were about 3 times more likely to start menstruating before their 12th birthday.
Previous studies have shown overweight girls tend to enter puberty at an earlier age and children of obese women tend to be overweight themselves, Dr. Sarah A. Keim, of the National Institutes of Health in Bethesda, Maryland, and colleagues note in the journal Epidemiology.
In the current study, daughters of obese mothers were more likely to begin menstruation at a young age, "even if they themselves were not overweight," Keim told Reuters Health in an email correspondence.
Keim's group interviewed 597 women between 22 and 32 years old to determine the age they began menstruation. Overall, 121 of the daughters reported first menstruation at age 11 or younger, while 158, 147, and 171 reported the same at the ages of 12, 13, and 14 years or older, respectively.
They compared this information with the mothers' pre pregnancy weight, height, and other information recorded when the moms participated in the 1959 to 1966 Collaborative Perinatal Project.
Daughters of mothers who were obese were 3.3 times more likely to begin menstruating when younger than 12 years old, relative to daughters of women who were not obese.
Menstruation at age 12 was 2.7-times more likely among daughters of obese women. These associations held in analyses that allowed for mothers' height and other factors linked with early menstruation.
By contrast, the investigators found no early menstruation link in the daughters of women who were normal or underweight when they got pregnant.
The researchers call for further investigations to explain these associations. For example, mothers and daughters may share diet and exercise habits. Or, as Keim pointed out, carrying excess weight during pregnancy may alter fetal development "in ways we are still trying to understand."