Preterm birth, which is delivery before 37 weeks of pregnancy, is a serious health problem. The researchers reviewed eight years of birth certificate and hospital discharge information for 2,885 preterm babies considered small for gestational age. Cesarean sections are often performed for babies diagnosed with intrauterine growth restriction who are not growing adequately in the womb. Babies delivered by a C-section before 34 weeks of pregnancy who were small for gestational age had higher odds of developing respiratory distress syndrome than babies born vaginally at a similar gestational age. The increased odds persisted after controlling for maternal age, ethnicity, education, primary insurance payer, pre-pregnancy weight, gestational age at delivery, diabetes and hypertension. Cesarean section delivery, which was thought to be harmless, is associated with breathing problems in preterm babies who are small for gestational age.