Gaudet said that experts think breast tissue is more susceptible to toxic exposures before a woman gives birth the first time compared to after.
The study finding, Gaudet said, ''provides additional motivation for young women who are thinking of starting to smoke not to." Those who smoked while young and gave up the habit still had a higher risk of breast cancer, she said, than never smokers.
To learn more about smoking and cancer, visit the American Cancer Society.
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