Weight influences timing of first menstrual period

Overweight and obese girls start menstruating months earlier than normal-weight girls, a Danish cohort study reports; however, their mothers’ prepregnancy weight influences the timing of menarche less than previously thought.

Researchers analyzed data on body mass index (BMI) and age at menarche from 3,169 Danish girls born between 1984 and 1987 as well as their mothers’ prepregnancy BMI. On average, the girls reached menarche about 25 days earlier for each 1-point increase in BMI (equivalent to about 6 pounds for females of average height and weight). For each unit increase in maternal BMI, age of menarche (AOM) occurred about 1 week earlier in the daughter.

After adjusting for covariates, the data “indicated a weak inverse association between maternal BMI and AOM and a much stronger inverse association between offspring BMI and AOM independent of maternal BMI,” the authors write. “We found no strong support for a programming effect of maternal prepregnancy BMI on AOM, but a small effect cannot be ruled out.” For the daughters, however, “the results indicate that…BMI plays an important role in accelerating AOM independent of the mother’s prepregnancy BMI.”

Overweight and obese girls began menstruating 3 to 5 months earlier than normal-weight girls, says study co-author Anshu Shrestha, MPH. The researchers conclude that “given the continuing obesity epidemic that starts in childhood, we expect a continuing decline in AOM in many countries worldwide.”

The study was published online March 10 in Fertility and Sterility.