In 1963, 16 out of every 100,000 women in Sweden developed breast cancer during or shortly after their pregnancies. Today, the figure stands at 37 per 100,000.
The researchers attributed the increase in pregnancy-associated breast cancer in part to the postponement of childbearing to an older age. Since the 1970s, the median age of first time mothers has increased by five years, from 24 to 29 years of age.
“The increase we see is a reflection of the fact that many women choose to delay having children,” said Dr. Mats Lambe from the Karolinska Institutet, to the Svenska Dagbladet (SvD) newspaper.
Together with Therese Andersson, Lambe was the lead researcher in the study, the results of which have been published in the latest issue of the journal of the American College of Obstetricians and Gynecologists.
Pregnancy in and of itself doesn't automatically bring about an increased risk for cancer. Rather, women actually have better protection against cancer with each child they have.
However, their breast cancer symptoms can worsen compared to those exhibited by non-pregnant women, because lumps can sometimes be interpreted as pregnancy related, rather than a sign of cancer, according to SvD.
The findings suggest, therefore, that breast cancer is underdiagnosed during pregnancy and lactation.