Objective: To introduce the effect of a single course of betamethasone for pregnant women at risk of preterm delivery (PTD). Materials and methods: In this study, a single course of 12 mg Bethamethasone was administered twice in 24 h (between 24-34 gestational weeks) for antenatal corticosteroid prophylaxis. Four hundred ninety-three neonates fulfilled the inclusion criteria and they were categorized (259 singletons, 192 twins and 42 triplets who met the inclusion criteria) into two groups according to the utilization of antenatal corticosteroid as control (n = 202) and study (n = 291) groups. We used respiratory distress syndrome (RDS), congenital pneumonia, intraventricular hemorrhage (IVH), neonatal sepsis, and bronchopulmonary dysplasia (BPD) as primary outcomes for the evaluation of neonatal morbidity. Results: Study and control groups were similar in terms of clinical characteristics. RDS, congenital pneumonia, neonatal sepsis, and BPD rates were significantly higher in the study group (betamethasone) (p = .05, p = .007, 0.003, and 0.004, respectively) between 24-34 gestational weeks (when the neonates of multiple pregnancies were excluded from the analysis, we have demonstrated that congenital pneumonia (p = .033) and neonatal sepsis (p = .030) were still significantly higher in the betamethasone group). The neonates of 24-28 gestational weeks were compared separately and we demonstrated that RDS (p = .012), congenital pneumonia (p = .022), IVH (p = .044), neonatal sepsis (p = .023), and BPD (0.001) were also more frequent in the study group. When the 28-32 gestational week data were compared, IVH (p = .020) and neonatal sepsis (p = .017) were more frequent in the single course betamethasone users. However, we could not demonstrate a significant difference between the control and study groups between 32-34 gestational weeks in terms of the primary neonatal outcomes used in this study. Conclusion: Single course antenatal betamethasone administration may be ineffective on the respiratory complications of preterm and very preterm infants while it may be unfavorable for extremely preterm infants. What is new about the paper, what could add to the current knowledge: Pregnant women at risk for preterm labor must be under intensive antenatal care programs, and if possible, necessary precautions must be undertaken to prevent fetal hypoxia together with etiology specific treatments. This approach might contribute to better perinatal outcomes than just administering antenatal corticosteroid therapy.