BACKGROUND Several studies suggested an association between first trimester biochemical markers (PAPP-A and ß-HCG) and infants below 10th percentile. Our goal was to describe this relationship of biochemical markers with small-for-gestational-age fetuses in our population. METHODS Retrospective analytic study of 2 035 pregnant women that underwent first-trimester screening in the period between March 2009 and September 2011. Small-for-gestational-age infants below 10th percentile were compared with control group (term newborn with birth weight above 10th percentile). Infants below 3rd percentile and control group were also compared. Multiple and logistic regression analysis were done with PAPP-A, ß-HCG (multiples of the expected normal median) and demographic maternal characteristics (ethnicity, weight and smoker status). RESULTS This study demonstrated an independent contribution of PAPP-A, maternal weight and smoker status in predicting small-for-gestational-age infants. For PAPP-A, the odds ratio for small-for-gestational age below 10th and 3rd percentile was 2.41 and 3.41, respectively (p < 0.01). For ß-HCG, odds ratio below 10th percentile was 1.70 (p = 0.03) and for birth weight below the 3rd percentile, the odds ratio was 3.22 (p < 0.01). CONCLUSIONS Low levels of PAPP-A and ß-HCG (values below 5th percentile of the study population) were associated with an increased risk of small-for-gestational-age infants in the pregnant population included in this study.