Ethyl linoleate in meconium: a biomarker for prenatal ethanol exposure

Abstract

Background: Fetal alcohol syndrome, fetal alcohol effects, alcohol-related neurodevelopmental disorder, and alcohol-related birth defects, all terms referring to the spectrum of consequences of in utero exposure to ethanol, are a major public health burden. There is currently no laboratory test to identify newborns exposed to ethanol in utero. Meconium was analyzed for ethyl linoleate, a metabolite of ethanol, as a biological marker for fetal ethanol exposure.

Methods: Samples of meconium were obtained from 248 infants and analyzed for fatty acid ethyl esters. Detailed maternal alcohol, tobacco, and drug use histories were obtained within 1 month of giving birth.

Results: The detection of ethyl linoleate in meconium was called a positive test. The mean number of drinks reported per week in the month before pregnancy, the first trimester, and overall were significantly higher in the positive group (unadjusted: 9.2 +/- 1.9 vs. 4.3 +/- 1.4, p = 0.004; 7.3 +/- 1.7 vs. 3.8 +/- 1.2, p = 0.03; and 6.1 +/- 1.3 vs. 3.0 +/- 1.0, p = 0.006). A positive test was not associated with marijuana, cocaine, or tobacco use. Sensitivity and specificity of the test were 72% and 51% to distinguish women who reported 1 or more drinks/week in the third trimester from women who denied use, and 68% and 48% to distinguish women who used > or =1 drink/week from women who used <1 drink/week in the month before pregnancy.

Conclusions: The presence of ethyl linoleate in meconium is the first reported biological marker for maternal ethanol use during pregnancy. Because of the inherent inaccuracy associated with the use of self-reporting, the establishment of true values of sensitivity and specificity will require validation where the presence, quantity, and timing of exposure to alcohol is known. Further validation of this marker will permit identification and intervention of at-risk infants.

Fig. 1.

Gas chromatograms of four representative meconium samples. The internal standard, ethyl heptadecanoate. is labeled 17:0. Chromatogram A is strongly positive for FAEE. Present are ethyl laurate (12:0). ethyl myristate (14:0), ethyl palmitate (16:0), ethyl oleate (18:1), ethyl linoleate (18:2), and ethyl linolenate (18:3). There is predominance of ethyl linoleate. Chromatogram B is a positive chromatogram with small peaks of 16:0, 18:1. 18:2, and 18:3. Chromatogram C is a positive chromatogram with a small peak of 18:2. Chromatogram D is negative with no peaks eluting with retention times similar to FAEE.

Fig. 2.

Dose of substance use ± standard error per trimester and month prior to pergnancy for women whose infants had a positive or negative meconium test. To estimate the amount of aicohol used, the number of drinks consumed per drinking day was computed based on the amount of beer, wine, or hard liquor consumed per drinking day with 12 oz of beer, 4 oz of wine, or 1 oz of hard liquor equivalent to one drink (0.5 ounces of absolute alcohol). For tobacco, the number of cigarettes smoked per day was recorded and for marijuana, the number of joints smoked per day of marijuana use was recorded. For cocaine, the number of rocks smoked per day was obtained. The frequency of use of alcohol, cocaine, and marijuana was estimated on a Likert type scale rangijng from 0 (less than once per month) to 7 (daily use). The frequency of use was multiplied by the amount used per day to compute an estimated dose per week for the month prior to pregnancy and for each trimester (referred to as dose/week). This score was then averaged for a total score for the prenatal exposure for each drug. For tobacco, it was assumed that the same number of cigarettes were smoked each day. The alcohol, marijuana, cocaine, and tobacco doses were plotted on a logarithmic scale after adding 1 to improve skewness and kurtosis (Jacobson et al„ 1996). p-values were calculated by Student’s two tailed t test.