For every additional drink a day on average during those early months, there were increased risks of 25% for smooth philtrum, 22% for thin vermilion, 18% for reduced birth length, 16% for lower birth weight, and 12% for microcephaly, reported Haruna Sawada Feldman, PhD, MPH, of the University of California San Diego in La Jolla, and colleagues.
There were similar findings for each additional episode of binge drinking and each additional drink in the maximum number consumed per occasion, the authors noted in the study, which appeared online ahead of print in Alcoholism: Clinical and Experimental Research.
Fetal Alcohol Syndrome (FAS)
Although FAS was first identified in 1973, little is known about the specific dose and timing of exposure to alcohol that increases the risk for birth defects. To further clarify the issue, researchers undertook a prospective study involving 992 women.
Data for the study was obtained from women enrolled in the California Teratogen Information Service and Clinical Research Program from 1978 to 2005. After getting counseling, women who reported exposure to at least 1 of 70 different agents, including alcohol, were interviewed in greater detail.
Pregnant women who reported no exposure to these agents were also asked if they would like to participate in the study.
At the end of the pregnancy, various outcome data were obtained. Timing of exposures was evaluated at 0 to 6 weeks after conception, 6 to 12 weeks following conception and then in the second and third trimesters.
For all live births, mothers were asked to participate in a standardized, blinded dysmorphological assessment of the child. The assessors, who were blinded for mother's status, looked for a standardized checklist of 132 malformations. Multiple gestations were excluded and, if the women had more than one pregnancy, only the first eligible birth was included in the analysis.
When women consuming one or more drinks per day were compared to those consuming less alcoholic drinks during the first trimester, higher risk was seen with higher dose for microcephaly, thin vermillion border, and smooth philtrum, as well as reduced birth length and weight. These outcomes did not exclusively occur in the higher-dose group, the researchers noted. During the second trimester, significant associations were seen with smooth philtrum, and weight and length. By the last trimester, only birth length was associated with average drinks per day and maximum number at one occasion.
Higher prenatal exposure to alcohol was significantly associated with incidence of smooth philtrum, but not with short palpebral fissures. The strongest associations were found during the second half of the first trimester in both average drinks per day (RR: 1.25; 95% CI 1.14 to 1.36) and maximum number of drinks in one episode (RR: 1.17; 95% CI: 1.09 to 1.26),
Nonlinear relationships for the various outcomes measured did not show evidence of clustering, and quadratic models constructed showed no nonlinear relationships. There was no indication of any safe level of alcohol exposure, the authors noted.
Among the limitations of the study was that its participants were volunteers and may not be representative of the population. In addition, the use of maternal reports of alcohol consumption may have led to an underreporting or misreporting of consumption.
"Based on our findings, there is no safe threshold for alcohol consumption during pregnancy with respect to selected alcohol-related physical features," the authors concluded. "Women who are of childbearing age and who are contemplating or at risk for becoming pregnant should be encouraged to avoid drinking, and women who are pregnant should abstain from alcohol throughout the pregnancy."
Reference: Feldmen HS, et al "Parental alcohol exposure pattern and alcohol-related birth defects and growth deficiencies: A prospective study" Alcohol Clin Exp Res 2012; DOI: 10.111/j.1530-0277.2011.01664.x.