A study has found that greater levels of drinking before a first pregnancy heighten the risk of cancer, research suggests.
Women who never have children, or delay becoming pregnant, were already known to be more susceptible to breast cancer.
The new research, based on findings from 91,000 women aged 15 to 40, found an additional link with alcohol intake between the start of menstrual periods and first pregnancy.
A woman’s breast tissue is believed to be especially sensitive to cancer triggers during this time.
Alcohol consumption between menarche - or first period - and first pregnancy also raised the risk of benign breast disease (BBD).
In both cases a dose response was seen. The more women drank, the more their risk of disease increased.
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.”
Every 10 gram per day increase in alcohol consumption raised the risk of breast cancer by 11%.
For women with an intake of at least 15 grams of alcohol per day - roughly two units or a medium sized glass of wine in the UK - the risk was 34% higher than for non-drinkers.
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.
The evidence suggested that alcohol consumed before first pregnancy may play an important role in the development of breast cancer, said the researchers.
“Reducing alcohol consumption during this period may be an effective prevention strategy,” they concluded.
<http://jnci.oxfordjournals.org/content/early/2013/08/26/jnci.djt259.full?sid=177c2330-d9fe-485f-827d-6a30a2fea986> (Journal of the National Cancer Institute, doi: 10.1093/jnci/djt259)