Background Given the challenges of confirming prenatal alcohol exposure ( PAE) during pregnancy using currently established biomarkers of alcohol consumption, we examined whether serum micro RNAs (mi RNAs) may serve as stable biomarkers for PAE. Alterations in the levels of specific circulating mi RNAs have been associated with various disease states and in animal models of fetal alcohol spectrum disorder. Methods Pregnant women in this prospective study were recruited from substance abuse and general maternity clinics affiliated with the University of New Mexico. Serum was collected at the time of admission for delivery from 14 subjects who reported ≥1 binge-drinking episode or ≥3 drinks/wk during pregnancy and 16 subjects who reported abstinence during pregnancy and tested negative for 5 ethanol biomarkers. Total RNA was isolated from serum and used for microarray analysis. Results False discovery rate-corrected analyses of covariance revealed that 55 mi RNAs were significantly altered between the 2 groups. Hierarchical clustering using only the significantly altered mi RNAs grouped samples into alcohol-consuming and non-alcohol-consuming individuals. Discriminant analysis then identified miRs-122*, -126, -216b, -221*, -3119, -3942-5p, -4704-3p, -4743, -514-5p, and -602 as the top 10 discriminators between the 2 groups. Ingenuity Pathway Analysis of putative mi RNA targets illustrated that mi RNAs identified in this study are involved in biological pathways that mediate the effects of alcohol, such as brain-derived neurotrophic factor, ERK1/2, and PI3K/ AKT signaling. Conclusions This is the first report of alterations in serum mi RNA expression that are associated with alcohol use during human pregnancy. These results suggest that serum mi RNAs could be useful as biomarkers of alcohol exposure. [ABSTRACT FROM AUTHOR]