10 doctors weighed in:
How does having a baby lower the risk of breast cancer in women?
10 doctors weighed in

Dr. Joseph Woods
Pathology
7 doctors agree
In brief: Less cycles.
Early menopause, late menarche and first full term pregnancy by age 18 lower the risk of breast cancer.
This is apparently done because the number of menstrual cycles is lowered over a woman's life by these factors. This lowers a woman's exposure to endogenous hormones, like estrogen.

In brief: Less cycles.
Early menopause, late menarche and first full term pregnancy by age 18 lower the risk of breast cancer.
This is apparently done because the number of menstrual cycles is lowered over a woman's life by these factors. This lowers a woman's exposure to endogenous hormones, like estrogen.
Dr. Joseph Woods
Dr. Joseph Woods
Thank
2 comments
Dr. Carlo Contreras
Nobody knows the precise answer. What is interesting is that even 1 pregnancy significantly reduces the risk of breast cancer. If the reason were number of cycles alone, a single pregnancy (9-15 total cycles) is a minimal amount of time considering that women menstruate for typically 25 years or so. So there must be other factors at play as well.
2 doctors agree
In brief: Less estrogen
The placenta puts out progesterone, which acts as an estrogen antagonist (off switch) in the body, to prevent ovulation while you're pregnant.
The cyclic ramp up in estrogen is also avoided. This period of lower estrogen exposure lowers overall cancer risk.

In brief: Less estrogen
The placenta puts out progesterone, which acts as an estrogen antagonist (off switch) in the body, to prevent ovulation while you're pregnant.
The cyclic ramp up in estrogen is also avoided. This period of lower estrogen exposure lowers overall cancer risk.
Dr. Scott Welker
Dr. Scott Welker
Thank
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