A new study pinpoints the latter half of the first trimester as a critical time in pregnancy for the vunerability to Fetal Alcohol Syndrome (FAS). The authors say their study is one of the first to examine the impact of quantity, frequency and timing of alcohol exposure on FAS, which is thought to affect about 1% of the US population and can result in physical, behavioural and learning problems. People with the syndrome may have abnormal facial features, such as a smooth ridge between the nose and upper lip, small head size, unusually small-set eyes and shorter-than-average height.
The 992 women in the study were enrolled in the California Teratogen Information Service and Clinical Research Program between 1978 and 2005, which provided confidential risk assessments for any potential toxin exposures during pregnancy. Every three months during the remainder of their pregnancies, they were asked about their use of alcohol and other substances, including specific dates of use, drinks per day, number of binge episodes and maximum number of drinks.
Information about their babies’ development was collected after birth, and each newborn was then examined by a dysmorphologist, a specialist in structural birth defects, to look for evidence of fetal alcohol syndrome as well as other conditions.
While higher levels of alcohol exposure were strongly linked to a greater risk of infants born smaller and lighter, with small heads and a smooth ridge between the nose and upper lip, the most significant associations were observed during the second half of the first trimester of pregnancy - defined as 43 to 84 days after conception.
For every one-drink increase in the daily average number of drinks consumed during this stage of pregnancy, there was a 25% higher risk for having a smooth ridge between the nose and upper lip; a 22% higher chance of having an abnormally thin upper lip; a 12% elevated risk of having a smaller-than-normal head; a 16% greater risk of reduced birth weight; and an 18% higher chance of reduced birth length. Drinking in any trimester was associated with greater likelihood of shorter birth length, the study found.
Study authors stressed that their research illustrates there is no safe amount of drinking during pregnancy, since the amount of drinking that produced these features in infants varied from woman to woman.
Study author Christina Chambers, an associate professor of pediatrics and family and preventive medicine at the University of California, San Diego commented. “Not every child of women who drink (even very heavily) has all the features, so there are certain susceptibility factors that we don’t know.”
Chambers and her colleagues theorised that alcohol exposure in the first six weeks of pregnancy, when many women don’t yet know they’re pregnant, may result in higher miscarriage rates, although the study did not include women who had miscarriages or stillbirths.
The study appears online Jan. 16 ahead of print publication in the April issue of the journal Alcoholism: Clinical & Experimental Research