Risk of breast cancer if you gain weight in adulthood and delay in your first childbirth ↑
May 12, 2025
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Dr. Lee Malcolmson's team at Manchester University in the UK surveyed 48,000 women who were screened for breast cancer in the UK.
According to the research team, previous studies have shown that weight gain in adulthood increases the risk of developing postmenopausal breast cancer, and some studies show that the earlier the first pregnancy, the lower the risk of breast cancer. In addition, a review of 21 studies on breast cancer and childbirth-related risk factors showed that for each 1 year increase in the first gestational age, the risk of premenopausal breast cancer increased by 5% and the risk of postmenopausal breast cancer by 3%. However, it is pointed out that it is not clear whether the combined effect of the two factors and the effect of weight gain on breast cancer will decrease when the first pregnancy period arrives.
The research team analyzed data from the cohort study (PROCAS) involving 48,417 women (median age of 57 years, median body mass index of 26.3 kg/㎡) who underwent breast cancer screening between 2009 and 2015. Women were divided into pre-30 and post-30 groups and post-30 groups according to their first gestational period and birth status, and body weight changes at 20 years old and pre-30 years old were investigated, followed by breast cancer development for an average of 6.4 years. During the follow-up period, 1,702 people were diagnosed with breast cancer.
As a result of the analysis, women who gained more than 30% of their weight after the age of 20, and who had their first childbirth after the age of 30 or who had not given birth had a 2.73 times higher risk of breast cancer than women who gave birth before the age of 30 and gained less than 5% of their weight. In addition, previous studies have also confirmed that early pregnancy has a protective effect against postmenopausal breast cancer, and that weight gain in adulthood is associated with increased risk of breast cancer.
In the UK, the proportion of obese and overweight women increased from 49% in 1993 to 59% in 2021 and, with the age of first childbirth delayed, the breast cancer diagnosis rate of women is at an all-time high.
The research team, however, found no evidence that the early pregnancy of the first trimester lowered the risk of breast cancer due to weight gain.
This article was translated by Naver AI translator.
