A breast cancer diagnosis is rare if you are a woman 45 years of age or under. However, of the 25,000 cases of breast cancer in women in this age bracket, one-third of them are postpartum mothers. For unknown reasons, the risk of breast cancer goes up in the first five years postpartum.
“It’s likely that the hormones of pregnancy play a role, says Eric Winer, director of breast oncology at Boston’s Dana-Farber Cancer Institute. For example, hormonal surges and fluctuations may speed up the growth of a pre-existing cancer, leading a woman to be diagnosed sooner than she might have been if she had never been pregnant.” (Source)