Women who consume more alcohol before their first pregnancy may have an increased risk of breast cancer, according to new research.
A study has found that greater levels of drinking before a first pregnancy could heighten the risk of the disease.
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, where a woman's breast tissue is believed to be especially sensitive during this period.
Scientists used data from the Nurses Health Study II, which looked at health and lifestyle in female registered nurses.
Women who never have children, or delay becoming pregnant, were already known to be more susceptible to breast cancer.
The evidence suggested that alcohol consumed before a woman's first pregnancy may play an important role in the development of breast cancer.
Consuming alcohol between 'menarche', the first period, and the first pregnancy also heightened the risk of benign breast disease.
Every 10 gram per day increase in alcohol consumption raised the risk of breast cancer by 11 per cent.
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 per cent 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 per cent and 81 per cent increased risk of breast cancer and proliferative BBD in our analysis respectively.”