Week 34 of Pregnancy Reduces Breast Cancer Risk: Study

Furthermore, the "34th week of pregnancy effect" doesn't only come with your first child.

Every week of pregnancy is special. But the 34th week of pregnancy is extra special because it has the power to protect you against breast cancer!

The 34th week of pregnancy lessens the risk of future breast cancer, say scientists

It’s well-known that women are less likely to get breast cancer later on after they give birth to a baby.

However, recently, scientists from Denmark and Norway have discovered the exact week in pregnancy that gives mums-to-be this benefit.

The study, published in the Journal Nature communications, showed that the 34th week of pregnancy causes significant changes to a pregnant woman’s body. So much so that it makes them less likely to get breast cancer in the future, says scientists.

Mads Melbye is the study’s lead author and is from the University of Copenhagen’s Department of Clinical Medicine. According to him, giving birth to a child at the 33rd week of pregnancy wouldn’t confer the “bonus of having a lower risk of breast cancer for the rest of your life.”

“It’s a very distinct change in risk when you go from week 33 to week 34,” he stresses.

Normal pregnancies last 40 weeks, and babies who are born earlier than their 37th week are premature.

The 34th week of pregnancy helps protect mums from breast cancer, scientists find. | Image Source: Stock Photo

How scientists conducted the study

Melbye and his group of researchers analysed data from a whopping four million women residing in Denmark and Norway, extending 40 years into the past.

The data showed three key pieces of information:

how old each woman was they delivered their child
the stage of pregnancy they were in when they gave birth
and if these women suffered from breast cancer in the future.

Scientists found that expecting mums who delivered their babies from the 34th week of pregnancy onwards, had, in general, a 13.6 percent lower risk of suffering breast cancer, compared to women who didn’t give birth to kids.

Scientists also found that while giving birth seven days before the 34th week did lower the risk, it wasn’t much: only 2.4 percent.

Melbye still doesn’t know exactly what happens in the 34th week of pregnancy that offers this benefit. Still, he says that pinpointing the 34th week of pregnancy “makes it much easier for researchers to focus” on the limited period where women’s bodies undergo a notable change.

In fact, Melbye thinks it’s possible for a pregnant woman’s body to send signals during the 34th week of pregnancy to heighten immune responses against causes of breast cancer in the environment.

“To the best of our knowledge it must have something to do with a specific biological effect that the cells reach during the 34th week of pregnancy,” he says.

The 34th week of pregnancy effect doesn’t come only from the first child

The benefit which you get from the 34th week of pregnancy also protects you against breast cancer if your second child is born past the 34th week of pregnancy. | Image Source: Stock Photo

Scientists have long known that pregnancy does help to lessen the risk of breast cancer. The reason is likely because breast cells change their basic composition once a woman becomes pregnant and begin to lactate.

Surprisingly, Melbye and his team found that the effect didn’t stop at the first delivery. Subsequent pregnancies that continued beyond the 34th week of pregnancy also lessened the risk of breast cancer all the more.

The “34th week of pregnancy effect” was still visible even when women had stillbirths at the 34th week of pregnancy. This suggests that the effect is probably not linked to breastfeeding.

There’s just one slight drawback, though. Researchers discovered that the benefit from the 34th week of pregnancy against breast cancer doesn’t happen when women are older than 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: You have to have your kids before you turn 29,” said Melbye.

“After that age there’s no extra bonus in breast cancer risk (reduction).”

Other ways to reduce the risk of breast cancer

Breastfeeding. Studies have shown can lessen the risk of contracting breast cancer. According to scientists, breasts aren’t developed until they are used for breastfeeding. Undeveloped breasts, in turn, are prime candidates for cancer, since it attacks undeveloped cells in the breasts, says researchers. And it doesn’t have to be long – even breastfeeding for short periods of time can lessen the risk of certain aggressive tumors by as much as 20%.
Be healthy. To lower the risk of non-hereditary breast cancer, Dr Esther Chuwa, a surgeon specialising in Breast diseases and Medical Director at the Esther Chuwa BreastCare Practice, Gleneagles Hospital, advises mums to abstain from smoking and alcohol. Furthermore, she says that maintaining a healthy and active lifestyle might also lessen the risk.
Screen your breasts routinely once you’re above 40. Ultimately, Dr Chuwa also reminds mums to self-examine your breasts once a month. Screening them via mammography once you turn 40 will also help to detect cancers early, which is the best chance at protecting yourself before it’s too late.

References: Nature Communications

Kevin Wijaya Oey

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