Having Children Before Age 30
Cuts Breast Cancer Risk

NEW YORK (Reuters Health) - While experts already know that a woman who has her first child by age 30 has a lower risk of breast cancer than her peers, new research suggests that the risk continues to decline with each child a woman has at a young age.

In a large study of Danish women born between 1935 and 1978, researchers found that among those who had their first baby by age 25, breast cancer risk declined with each additional child they had before age 30. In addition, the investigators found that--compared with younger women with children--a woman's cancer risk was higher the older she was for not only her first birth, but also later ones.

Research has shown that when a woman either has no children or has her first child at a later age, her risk of breast cancer is higher than that of a woman who has a child at a younger age.

Similarly, women who started their menstrual periods earlier in life appear to have an elevated risk compared with those who started menstruating at an older age. The link between both menstruation, child bearing and breast cancer appears to be estrogen. It is thought that the longer the exposure to high levels of the hormone, the greater the breast cancer risk.

The timing of estrogen exposure seems vital as well. A woman's early reproductive years may be a ``critical time window'' in which any births cut the long-term risk of breast cancer, Wohlfahrt and Melbye write.

In the study, the researchers examined national health data on about 1.5 million Danish women, more than 13,000 of whom developed breast cancer by the end of the study follow-up. For every 5-year increase in age at a woman's first, second, third and fourth birth, her breast cancer risk climbed roughly 8% compared with women who had the same number of children at a younger age.

In general, women who have more children are at lower risk of breast cancer than other women, but the findings suggest this is true only for those who have all their children at a relatively young age. Multiple childbirths later in life ''evidently induce no reduction in risk,'' the authors note.

SOURCE: Epidemiology 2001;12:68-73.
Reference Source 89

For more information on prevention topics for this and other conditions, use
PreventDisease.com's "Quick Prevention Resources".