Aim: To analyze second trimester risk factors to predict small for gestational age and intrauterine growth restriction (IUGR) fetuses. Materials and Methods: The authors retrospectively analyzed clinical files of 5,390 women, who delivered between 2007 and 2009, 4,071 of which were included in the study. Adequate for gestational age (AGA), small for gestational age (SGA), and IUGR fetuses were included. Results: The authors found IUGR to be delivered significantly earlier than SGA and AGA. Moreover, they found a higher prevalence of nulliparity in SGA and IUGR fetuses than in AGA, and a significant higher prevalence of bilateral notch in SGA than AGA. SGA fetuses at 20 gestational weeks present a significantly higher value of umbilical artery pulsatility index (PI) and mean uterine arteries resistance index (RI) than AGA. In multivariate logistic regression analysis, the second trimester factors to predict SGA at delivery were: mother age, nulliparity, academic title, umbilical artery PI at 20 gestational weeks, mean RI of uterine arteries, and bilateral notch. In case of IUGR the most predictive factors were: mother age, nulliparity, and bilateral notch at 20 gestational weeks. Conclusions: Clinical interview and sonographic examination at 20 gestational weeks were capable to predict fetal growth potential.