Self-reported history of breastfeeding in relation to recalled age at menarche in the United States.

Menarche is a key life history event that shapes the female reproductive trajectory and is important to the study of human biology because of the associated epidemiological and social consequences later in life. Our question is whether breastfeeding is associated with the variation in timing of menarche. Using data from a college-aged female student population from Amherst, MA, we examined whether having been breastfed was associated with age at menarche. Of the 340 female participants with information on breastfeeding during infancy, we found that women who were breastfed (n = 286) had an adjusted mean age of menarche of 12.53 years (SE 0.09), while those who were not breastfed (n = 54) had an adjusted mean age of menarche of 12.04 years (SE 0.20; p < 0.03). We propose further research that explores a finer distinction between formula-fed, mixed-fed or predominantly breastfed infants, duration of breastfeeding and age at menarche.