Pregnancy May Increase Breast Cancer Risk Before Offering Protective B

Women who’ve given birth may be at an increased risk of breast cancer. That’s according to a new study in the Annals of Internal Medicine.

Researchers from the University of North Carolina Gillings School of Global Public Health looked at 15 different prospective studies involving more than 800,000 women under the age of 55, and found that while the risk is small, women who’ve given birth are more likely to develop breast cancer for up to 23 years after having their last child when compared to women who have not given birth.

According to the study, the highest risk occurred within the first five years after giving birth. Dr. Brian Czerniecki, chair and senior Member in the Moffitt Cancer Center Department of Breast Oncology says, “It’s complicated, but it’s true that women are at an increased risk of breast cancer for five to six years postpartum.”

The researchers found that even though breastfeeding did not appear to influence the findings, other factors did impact the results. These factors include the age at which a woman first gave birth, how many children she had and whether she had a family history of breast cancer did.

A study author says a reason for the increased risk of breast cancer may be due to the fact that pregnancy is a time when there is rapid development of the breast tissue. The cells in the breast are rapidly dividing, and when tissue is expanding quickly there's more potential for an error to occur within a cell or for an error that's already in a cell to multiply.

Later in life, the risks seemingly reverse. Twenty years after a full-term pregnancy, women who’d given birth were less likely to develop breast cancer than those who had never given birth.

According to the National Cancer Institute, pregnancy-related factors that lower the risk of breast cancer later in life include:

Having a first full-term pregnancy younger than 20
Having more than one birth
Having a history or preeclampsia
Breastfeeding for a long period of time

While factors that tend to increase the risk of pregnancy include:

Having your first full-term pregnancy over the age of 30
Giving birth within the past 10 years
Taking diethylstilbestrol, a synthetic form of estrogen, during pregnancy.

Researchers say the study was limited because any breast cancer diagnoses during pregnancy in the data were not uniformly distinguishable from diagnoses made during early postpartum. Also, the study was unable to look at the biological mechanisms behind why an association between breast cancer risk and childbirth even exists.

Study researchers caution that the risk is small and should not be a determining factor in deciding whether or not to get pregnant.

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