Women who deliver babies with a high birth weight have a more than double chance of developing breast cancer — compared to women who deliver babies with a lower weight.
That’s according to a finding that came after a study was conducted by the University of Texas (UT) Medical Branch at Galveston. The study observed more than 24 000 women who delivered babies with a birth weight of 3.72 kg or more.
Author of the study and professor of obstetrics and gynaecology in the Division of Maternal-Fetal Medicine at UT, Dr. Radek Bukowski, said that this increased risk is independent of other breast cancer risk factors.
According to Bukowski, this study is valuable for medical professionals.
“It’s important because if this [the finding] stands in further studies, it may have an impact on clinical tests for women, and may even improve [doctor’s] predictions,” he said.
Even though the study identified 3.72 kg as the weight of risk — Bukowski added that as the birth weight of babies increases, so too does a women’s likelihood of developing breast cancer.
Bukowski suggests that the hormonal environment that heavier babies create for moms, establishes a prosperous setting for the development of breast cancer. Although this risk was known to be independent of other factors, research from previous studies indicates that heavier mothers were also likely to have heavier babies.
Data from these sampled women was taken from two previous studies.
The first study
The first study by Bukowski and his team followed 410 women who participated in the Framingham Offspring Birth History Study.
These women were giving birth to their first child. The weight of their baby was monitored for 17 years and after this time, 31 women had been diagnosed with breast cancer. It was found that women whose baby’s weight was in the top quintile position had a 2.5 times higher risk of developing breast cancer, independent of other factors. Researchers also took other breast cancer risk factors into consideration, such as the women’s weight, family history or intake of hormones.
The results suggest that despite these other factors, there was still a strong relationship between heavy babies and an increased risk of developing breast cancer.
The second study
The other study included 23,824 women who participated in the First and Second Trimester Evaluation of Risk [FASTER] for Aneuploidy. Women who gave birth to one baby between 1999 and 2003 were observed. As part of the study, researchers studied the women’s blood samples — measuring levels of hormones such as estriol, alphafetoprotein [AFP] and PAPP-A, which occur during pregnancy — but are also hormones that encourage breast cancer.
From this study, it was found that women whose baby was 3.72 kg or heavier, had high levels of estrogen. They also had low levels of anti-estrogen. Bukowski calls these hormonal settings “pro-carcinogenic.”
“Women can’t alter their pregnancy hormones, but can take steps to increase their general protection against breast cancer,” stated Bukowski.
He suggests that breastfeeding, having more than one baby and leading an overall healthy lifestyle, could help reduce the likelihood of developing breast cancer. This he says, creates a discouraging hormonal environment, which may decrease mom’s risk.
Findings from the FASTER assessment suggest that women whose baby’s weight was in this top quintile position, faced a 25% chance of developing breast cancer, as they were likely to have the highest ratio of estriol to AFP as well as comparatively higher estrogen levels.
“It looks like during pregnancy, when a woman carries a big baby, the hormonal milieu favours breast cancer development,” said Bukowski.
According to Bukowski, findings from the study may explain why this occurs.
Authors of the study say, that just as animal studies suggest, breast stems cells which are associated to breast cancer, either increase or decrease in the presence of hormones. These hormones exist in instances of pregnancy.
Authors of the study have found that cells are able to retain the memory of previous exposure to hormones, which are higher for moms who give birth to a heavy baby. For this reason, these hormones occurring during pregnancy may lead to an increased chance of developing breast cancer at a later stage of the woman’s life.
Reducing mom’s risk
Bukowski hopes that this finding will shed more light on breast cancer predictions. By understanding the link between hormonal environments existing during pregnancy and breast cancer, doctors may have an impact on lowering mom’s risk. With the help of this study, women birthing heavy babies should adopt a favourable lifestyle for the sake of their health – whether it’s healthy eating, regularly exercising or even frequently going for cancer screening tests.
Bukowski says that the median age of diagnosis of breast cancer is 61. This means that it may take up to 38 years from the time baby is born for breast cancer to be diagnosed.
“If confirmed, this would be a predictor for breast cancer decades before it is diagnosed,” he said.
This time frame allows for caution to be exercised amongst moms of heavy babies. He also states that despite these findings, a further study is required.
“No matter how heavy their baby is, women can reduce the risk of breast cancer by cutting back on alcohol, keeping a healthy weight and staying physically active,” said Claire Knight, from Cancer Research [UK].
Although more research is needed, these findings should encourage moms to be more cautious about their baby’s weight and their chances of developing breast cancer.
According to this study, this relationship was found to be uninfluenced by other breast cancer risk factors. Despite this, studies show that heavier moms tend to have heavier babies. This means that by following a healthier lifestyle as advised by Bukowski and Knight, the likelihood of developing breast cancer may be reduced. This also includes going for frequent cancer screening tests. Most importantly, as noted by Bukowski, this link may be a predictor for breast cancer decades before it is diagnosed.