Sex differences in preterm respiratory morbidity: A recent whole-population study

Aim: To determine whether there were differences between male and female infants in respiratory morbidity in a whole population of extremely preterm infants, including infants born below 24 weeks of gestation.Methods: Retrospective whole-population study of all infants <28 weeks of gestation admitted to a neonatal unit in England from 2014 to 2019. Bronchopulmonary dysplasia (BPD) development was defined as any respiratory support at 36 weeks postmenstrual age.Results: The 11 844 infants had a median (IQR) gestational age of 26.0 (24.9-27.1) weeks and a birth weight of 0.81 (0.67-0.96) kg. The duration of invasive ventilation was longer in male compared to female infants who were born at 24-27 completed weeks of gestation (p < 0.001), but not significantly different between male and female infants born at 22 and 23 weeks of gestation (p = 0.446). The incidence of BPD was higher in male compared to female infants born at 24-27 weeks of gestation (p < 0.001) but not different between male and female infants born at 22 and 23 weeks of gestation (p = 0.148).Conclusion: Respiratory morbidity was more pronounced in male compared to female extremely preterms, only in gestations 24-27 completed weeks. Male predominance was absent in infants born below 24 weeks of gestation.