A new study - based on findings from 91,000 women - has found that greater levels of drinking before motherhood heightens the risk of the disease.
Every 10 grammes per day increase in alcohol consumption - just over one unit, or a small glass of wine - raised the risk of breast cancer by 11%.
For women with an intake of at least 15 grammes of alcohol per day - roughly two units or a medium sized glass of wine - the risk was 34% higher than for non-drinkers.
Writing in the Journal of the National Cancer Institute, the researchers led by Dr Ying Liu from Washington University School of Medicine in St Louis, US, said: "The longer the duration of menarche (first period) to first pregnancy, the higher is a woman's risk of breast cancer.
"Compared with non-drinkers with a shorter duration, non-drinkers with duration of 10 or more years between menarche and first pregnancy had 26% and 81% increased risk of breast cancer and proliferative BBD in our analysis respectively."
A woman's breast tissue is believed to be especially sensitive to cancer triggers between the start of menstrual periods and first pregnancy.
Women who never have children, or delay becoming pregnant, were already known to be more susceptible to breast cancer.
Alcohol consumption between menarche - or first period - and first pregnancy also raised the risk of benign breast disease (BBD), the research found.
The scientists used data from the Nurses' Health Study II, a major American study of health and lifestyle in female registered nurses.
Among those with a history of full-term pregnancy, 1,609 cases of breast cancer and 970 cases of BBD were recorded.
"Reducing alcohol consumption during this period may be an effective prevention strategy," the researchers concluded. (news.sky.com/story/1134459/breast-cance
интересно, считается только полносроковая беременность или аборт на ранних сроках тоже в зачет? если второе, то явно отрывающаяся молодежь себя качественно обезопашивает %)