Maternal smoking during pregnancy is a significant threat to the fetus. We examined the association between active maternal smoking and smoking cessation during early pregnancy with newborn somatometrics and adverse pregnancy outcomes including preterm delivery, low birth weight, and fetal growth restriction. One thousand four hundred mother–child pairs with extensive questionnaire data were followed up until delivery, within the context of a population-based mother–child cohort study (Rhea study), in Crete, Greece, 2007–2008. Comparing smokers to nonsmokers, the adjusted odds ratio (OR) was 2.8 [95% confidence interval (CI), 1.7, 4.6] for low birth weight and 2.6 (95%CI: 1.6, 4.2) for fetal growth restriction. This corresponded to a 119-g reduction in birth weight, a 0.53-cm reduction in length, and a 0.35-cm reduction in head circumference. Smoking cessation early during pregnancy modified significantly these pregnancy outcomes indicating the necessity for primary smoking prevention.