Aims: In current clinical practice, prenatal alcohol exposure is usually assessed by interviewing the pregnant woman by applying questionnaires. An alternative method for detecting alcohol use is to measure the biomarker carbohydrate-deficient transferrin (CDT). However, few studies measure CDT during pregnancy. This study examines the utility of CDT biomarker in the screening of alcohol exposure during early pregnancy. Methods: A cohort of 91, first-trimester pregnant women assigned to a public reference maternity hospital, was screened using the Green Page (GP) questionnaire, an environmental exposure tool. CDT levels and other biomarkers of alcohol use were measured and compared with questionnaire data. Results: About 70% of the mothers in the study consumed alcohol during early pregnancy and 22% met high-risk criteria for prenatal exposure to alcohol. CDT measurement showed a statistically significant area under the receiver operating characteristic curve with a value of 0.70. For a value of 0.95% of CDT, a specificity of 93% was observed. The most significant predictors of CDT were the number of binge drinking episodes, women's body mass index and European white race. Conclusion: Pregnant women with a CDT value >0.95% would be good candidates for the performance of the GP questionnaire during early pregnancy in order to detect potential high-risk pregnancy due to alcohol exposure.