New Research Identifies The Precise Week During Pregnancy That Reduces Breast Cancer Risk

There is a significant change that happens in a woman's body during a precise moment in her pregnancy that does something pretty incredible for her down the road. A recent study out of Norway and Denmark has pinpointed the 34th week of pregnancy as a moment of "striking change" that ultimately lowers a woman's risk for contracting breast cancer later in life.

Along with his team of researchers, study lead author Mads Melbye from the University of Copenhagen's Department of Clinical Medicine studied a database of nearly four million women in Denmark and Norway dating back almost 40 years. They looked at data such as the age at which each of the women gave birth, how far into a pregnancy each birth occurred, and whether or not they developed breast cancer later in life.

What they found was striking. Women who gave birth after 34 weeks had an average 13.6 per cent lower risk of developing breast cancer, compared to women who did not have any children. For pregnancies that ended just one week earlier - at 33 weeks - while there was still a reduction in risk, it was lowered to only 2.4 per cent.

"If you deliver a child at week 33 you get the child, which is great, but you don't get the bonus of having a lower risk of breast cancer for the rest of your life," said Melbye. He added that a "very distinct change" in risk happens when you go from week 33 to week 34.


Unfortunately, for now, what exactly changes in women during this particular week of gestation remains a mystery.

"To the best of our knowledge it must have something to do with a specific biological effect that the cells reach at 34 weeks," Melbye said. He did venture a guess, however, suggesting that it could be a woman's body sending a signal to boost immunity against environmental causes of breast cancer.

While many experts also believe that a correlation also exists between breastfeeding and a lowered risk of breast cancer, the study claims that this particular change is unlinked to breastfeeding. They found that even women who experienced stillbirths past the 34th week were still found to have a much lower risk of contracting breast cancer later on.

There is a catch, however.

According to Melbye, this lowered risk only occurs in women who have their children before the age of 30.

"It's not only the first childbirth; every childbirth has its own reduction in breast cancer risk but there's a trick to this," said Melbye. "You have to have your kids before you turn 29."

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