A new retrospective study has uncovered factors that increase the likelihood of early first period (menarche) among UK girls. Early menarche is known to increase the risk of breast cancer in adulthood, but, apart from weight, information on what induces early development among girls is limited. The study included 81,606 women aged 16 to 98 who were participants in the Breakthrough Generations Study.

When potential triggers were considered individually, first period was found to take place earlier in girls who had a low birth weight, were singletons (i.e., not twins or triplets), were exposed to maternal smoking while in the womb, had mothers with pre-eclampsia, were not breastfed, were non-white, were heavy compared to their peers at age seven, were tall compared to their peers at age seven, or got little exercise. First period took place later the greater the number of children in the family. Age of first period was inversely associated with birth order (the oldest girl tending to have a later first period than the youngest in a family). When the factors were combined in a multivariate model, birth weight, ethnicity, weight, height, participation in exercise, number of siblings and birth order remained statistically significant, and maternal age at birth became significant, with older mothers less likely to have daughters with early periods. The authors conclude that age at first period is influenced by both pre- and post-natal factors. These factors may in turn affect breast cancer risk.

Please see our article on how to protect our daughters from breast cancer for more information on how to protect girls during childhood and puberty from future breast cancer.