VARIABILITY OF SELF-REPORTED MEASURES OF ALCOHOL-CONSUMPTION - IMPLICATIONS FOR THE ASSOCIATION BETWEEN DRINKING IN PREGNANCY AND BIRTH-WEIGHT

Study objective-To describe the intrasubject variability of self repor ted maternal alcohol consumption using different ways of collecting in formation and to analyse the implications of this variability for rese arch into the effect of low to moderate maternal alcohol consumption o n birth weight. Design-This was a longitudinal study. Self reported ma ternal alcohol consumption before, during, and after pregnancy was ass essed on four occasions over two years. The data were collected by two self administered questionnaires and during two personal interviews ( one by phone and another face to face). Settings-The Obstetrics Depart ment, Odense University Hospital, Odense, Funen, Denmark. Participants -A total of 2880 pregnant women were recruited consecutively from the hospital catchment area. Altogether 328 pregnant women and their babie s were selected. All women who reported an average alcohol consumption of five drinks or more per week were recruited to the study (164 wome n) and a 1:1 control group was selected from the remaining women based upon two matching criteria: expected date of delivery and the women's year of birth. Some 279 women (85%) completed the study. Measurements and main results-self reported alcohol consumption (number of drinks per week) and birth weight (g) were the main outcomes. Women's self re ported alcohol consumption varied over time and according to the data collection method. When different methods of data collection were used to assess alcohol intake in similar periods of time, significant diff erences in reporting were found despite the relatively high correlatio ns between the measurements. Although a consistent reduction in birth weight with increasing consumption of alcohol was found, there were di fferences in the shape and strength of this association when comparing the six available alcohol measurements. Conclusions-The type of quest ions used, the way the data were collected, the period of time referre d to, and the time the questions were asked, should be taken into cons ideration when describing the drinking pattern of pregnant women. Furt hermore, birth weight results from studies that have used different al cohol measures should be interpreted or compared with caution because of possible large differences resulting from the differing methods of assessing fetal exposure to alcohol.