Blood groups have been shown to play an important role in a lot of diseases in various studies conducted in adults. The objective was to investigate whether there is a relationship between morbidities and ABO blood groups system in preterm infants. This retrospective cohort study included preterm neonates born at < 32 weeks of gestation with a birth weight < 1500 g. Neonates were grouped by blood type (O, A, B, AB) and morbidities of prematurity were compared among these groups. Data pertaining to 1785 very low birth weight preterm neonates were analyzed. Comparison of the A and non-A blood groups revealed that infants with blood group A had significantly higher incidence of patent ductus arteriosus (PDA) (48.7 % vs. 39.7 %, p = 0.005) and bronchopulmonary dysplasia (BPD) (27 % vs. 20.8 %, p = 0.04), while the incidence of grade ≥ 3 intraventricular hemorrhage was lower (5.1 % vs. 10.1 %, p = 0.006). This study represents the first and biggest series examination of the relationship between blood groups and preterm morbidities. Our results show that blood group A may be a risk factor for PDA and BPD.