Epidemiological evidence suggests that breastfeeding protects against breast cancer.
Whether an effect of age at first breastfeeding is independent of an effect of age at first birth is unclear.
We hypothesized that nausea and vomiting in pregnancy, which are associated with elevated serum oestradiol levels during pregnancy, may increase risk.
Cases were 452 parous, premenopausal women, 40 years or younger, diagnosed with breast cancer in Los Angeles County from July 1983 to December 1988.
Control subjects were matched to cases on age, race, parity and neighbourhood.
Pregnancy and breastfeeding histories were obtained from in-person interviews.
Odds of breast cancer among women who breastfed for at least 16 months relative to those among women who did not breasffeed was 0.66 [95% confidence interval (Cl) 0.41-1.05]. Number of children breastfed was not associated with risk.
Risk was lower in women who first breastfed at older ages.
Having ever been treated for nausea or vomiting during pregnancy was associated with an increased risk, especially in women experiencing recent pregnancies (OR=2.03,95% Cl 1.05-3.92).
These results support a protective role of breastfeeding and an adverse role of nausea or vomiting during pregnancy in the development of premenopausal breast cancer, especially in the years immediately following pregnancy.
Mots-clés Pascal : Tumeur maligne, Glande mammaire, Préménopause, Facteur risque, Epidémiologie, Gestation, Allaitement, Californie, Etats Unis, Amérique du Nord, Amérique, Etude cas témoin, Adulte jeune, Homme, Glande mammaire pathologie
Mots-clés Pascal anglais : Malignant tumor, Mammary gland, Premenopause, Risk factor, Epidemiology, Pregnancy, Breast feeding, California, United States, North America, America, Case control study, Young adult, Human, Mammary gland diseases
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Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 97-0354362
Code Inist : 002B20E02. Création : 12/09/1997.