Drinking while pregnant can harm the developing fetus, leading to physical, cognitive, and neurobehavioral effects that may persist into adulthood. No safe level of alcohol in pregnancy has been identified, and many guidelines now recommend total abstinence. However, prenatal drinking remains common, particularly early on before women are aware of their pregnancy.

Monitoring for alcohol use in pregnancy is important for targeting educational interventions. However, accurate detection of prenatal drinking is very difficult: women may under-report their drinking because of embarrassment or stigma, retrospective reporting is compromised by inaccurate recall, and healthcare providers vary in whether and how they screen for prenatal alcohol use.

Researchers from the University of Auckland in New Zealand have published a pilot study in the journal Alcoholism: Clinical and Experimental Research assessing the role of complementary tools for measuring alcohol use in a community antenatal setting. 

Over 300 pregnant women recruited from antenatal clinics in Auckland were screened for prenantal drinking using two tools. The first, an anonymous lifestyle questionnaire, included various questions about the pregnancy and alcohol usage before and after conception and pregnancy awareness. The second was a five-question screener on general drinking behavior around the time of conception.

Forty-six women who screened positive for prenatal alcohol use, and 35 women who did not, completed one or more face-to-face interviews with trained researchers during their pregnancy, and again within a week after giving birth.

Additionally, a biomarker of alcohol metabolism, called phosphatidylethanol (PEth), was measured in dried blood spot samples collected from their newborns during routine heel pricks. This test can detect alcohol exposure within the last month of gestation, although research is needed to fully validate its use in infants. 

The data showed that when pregnancy was unplanned, women became aware that they were pregnant later than in planned pregnancies, and were more likely to have drunk moderate-to-heavy amounts of alcohol before awareness. In early pregnancy, the five-question screener and face-to-face interviews were more likely to identify moderate-to-heavy alcohol use than the lifestyle questionnaire.

Only one woman reported regularly drinking at a moderate-to-heavy level after becoming aware that they were pregnant.

However, over 40% of newborns showed levels of the PEth biomarker that may be indicative of recent moderate-to-heavy exposure, with no association with maternal self-reported drinking (although the researchers note that PEth data in this pilot study were not cross-checked against other biomarkers or with maternal PEth levels).

The findings highlight the time before pregnancy awareness as a high-risk period for maternal drinking, and that educational messages should be reinforced as pregnancy progresses. Multiple tools may be needed to identify prenatal alcohol exposure at different points across pregnancy.

A quick, validated screener may be of value for identifying women at risk of an alcohol-exposed pregnancy. Sensitive interviewing appears better than in-depth questionnaires for detecting drinking in early pregnancy, but neither may be appropriate later on when social stigma around prenatal alcohol use is greater. In late pregnancy, use of an objective biomarker may be helpful for identifying those with babies at risk from prenatal alcohol exposure.