Pre-pregnancy drinking: how drink size affects risk assessment.

AIMS: We considered the role of drink size in determining average daily consumption among groups at risk for Fetal Alcohol Syndrome.
DESIGN: In-person hour-long interviews gathered cross-sectional retrospective data about drinking before an index pregnancy.
SETTING: Subjects were recruited at public clinics in Los Angeles and the San Francisco Bay area. To reach those not necessarily seeking prenatal care, community outreach in the same urban areas was undertaken. PARTICIPANTS: Three hundred and twenty-one pregnant women were interviewed: 102 Native Americans, 185 African Americans, and 34 Caucasians. MEASUREMENTS: Volume of drinking prior to pregnancy was assessed using the graduated frequency series, which asks respondents to specify their drinking in terms of standard drinks. Using vessel models and photographs, respondent-defined drink sizes were then determined, and volume was recalculated accordingly.
FINDINGS: For most beverages, the difference in milliliters between self-selected drink size and a standard size drink was significant, with the mean self-selected drink sizes ranging from 49% above the standard size (for beer) to 307% above the standard size (for spirits). For women whose pre-pregnancy average daily volume (ADV) was at the risk level of > or = 1 standard drink per day, ADV increased from four to almost 10 standard drinks per day when self-defined drink sizes were instead considered. Similarly, for women having three or more standard drinks a day, their daily dose of ethanol increased from 57 g to 153 g of ethanol per day.
CONCLUSIONS: If risk levels have been based on underestimates that assume women with alcohol-affected infants had standard drink sizes, then true risk levels may be higher than previously thought. Related, risk drinkers presenting at prenatal clinics may be missed if screening protocols do not ask about drink size.