November 24, 2010
Lifestyle and health factors starting from before birth may affect the age at which a girl begins her periods, a major new study published today in the British Journal of Cancer shows.
Scientists at The Institute of Cancer Research (ICR) found that mothers who smoke or suffer pre-eclampsia during pregnancy were more likely to have daughters who menstruated early. Other factors linked to early menstruation included having a low birth weight, being a singleton (not a twin), not being breastfed, having fewer siblings, having an early birth order (being an older sibling) and being non-white.
The study also confirmed that girls who were heavier or taller than other children at age seven and exercised little as children were more likely to start their first period at a young age.
Age at menarche (when periods begin) has long been established as a risk factor for breast cancer, possibly because these women are exposed to female sex hormones for a longer period of time. Disease risk gradually increases with progressively younger age at menarche and older age at menopause.
Analysis leader Danielle Morris, from the ICR, said: “This research shows that there are factors influencing age at first period that likely begin even before a child is born, yet might affect risk of developing breast cancer decades later.
“A girl who takes more exercise is likely to start her periods later in life. We know exercising regularly as an adult can help reduce the risk of developing breast cancer. This study shows that exercising as a child could also potentially have an effect on breast cancer risk later in life.”