While medical guidelines recommend complete abstinence, a large survey of women in the UK, Ireland, Australia and New Zealand finds drinking alcohol during pregnancy to be a prevalent practice.
The study in the online journal BMJ Open found the following ranges of proportions in alcohol use during pregnancy: 20-80% in Ireland and 40% upwards in the UK, Australia and New Zealand.
There were also high levels of binge drinking during pregnancy – over 45% in the Irish center of one of the cohorts.
The prevalence was consistent across social groups. However, women who smoked were found to be 17% more likely to drink during pregnancy.
A higher level of education, having other children, and being overweight or obese were, on the other hand, slightly predictive of a lower risk of drinking while pregnant.
The researchers made an analysis of data from three studies: The Growing up in Ireland (GUI) study, the Screening for Pregnancy Endpoints (SCOPE) study and the Pregnancy Risk Assessment Monitoring System (PRAMS).
A total of 17,244 women who had delivered live babies in the UK, Ireland, Australia and New Zealand were included in the analysis of the amounts and type of alcohol drunk before and during the gestation period.
The highest rates of drinking were in Ireland – with 90% drinking before pregnancy and 82% during gestation.
Ireland also had high rates of binge drinking – 59% before and 45% during pregnancy, based on estimates from the SCOPE study, although the researchers caution that lower rates were also found in some cohorts.
Measures of the amount of alcohol drunk ranged between 15% and 70% of the women saying that they had drunk 1-2 units a week during the first 3 months of their pregnancy.
Between the first and second trimester, however, the number of units drank dropped substantially in all countries, as did binge drinking levels.
The authors of the study issue a note of warning:
“Although low proportions of women engaged in heavy drinking, the adverse consequences of heavy alcohol consumption during pregnancy on birth outcomes, long-term gross motor function, and social, cognitive, emotional and behavioural outcomes in offspring make heavy gestational alcohol consumption a high public health priority.”
Most medical and government guidelines advise women to stop drinking during pregnancy, although the authors do note some evidence that 1-2 units up to twice a week is not harmful to the unborn baby.
Other findings of the study were that, compared with white women, those of other ethnicities were less likely to drink alcohol while pregnant.
Younger women were also less likely to drink while carrying an unborn baby than older women.
The researchers point out that poor evidence on the effects of gestational alcohol consumption and a subsequent lack of coherence in clinical and government guidelines “stem from a lack of biological markers of light or moderate alcohol use during pregnancy.”
Instead, associations with health outcomes rely on self-reported maternal alcohol consumption, which may be biased.