Smoking during pregnancy and breast cancer risk in very young women (United States).
OBJECTIVE
To evaluate the association of smoking during a woman's first pregnancy, a period of pronounced growth and differentiation of mammary tissue, and her subsequent breast cancer risk.


METHODS
In this matched case-control study, we used linked birth certificate and tumor registry data from the New York State Health Department. Cases were 319 women aged 26-45 who were diagnosed with breast cancer in New York State between 1989 and 1995 and who completed a first pregnancy in New York State after 1987 at least one year prior to diagnosis of cancer. Controls were 768 primiparous women matched to cases on county of residence and delivery date. Information on prenatal smoking and other factors characterizing the woman's first pregnancy was obtained from the pregnancy record of each subject, and the association of these factors to breast cancer risk was assessed using conditional logistic regression.


RESULTS
Smoking during pregnancy was associated with increased risk for breast cancer (crude OR = 2.7, 95% confidence interval (CI): 1.1-6.3). Adjustment for maternal age, subject age, race, and education strengthened this association (OR = 4.8, CI 1.6-14.6).


CONCLUSIONS
These findings suggest that cigarette smoking during a woman's first pregnancy may increase her risk for early-onset breast cancer.
Department of Preventive Medicine and Biometrics, University of Colorado Health Sciences Center, Denver 80262, USA.
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Innes
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Byers
D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D001943:Breast Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D016022:Case-Control Studies; D015897:Comorbidity; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009518:New York / Q000453:epidemiology; D016017:Odds Ratio; D011247:Pregnancy / Q000502:physiology*; D011248:Pregnancy Complications / Q000453:epidemiology*; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*