Gestation at birth, mode of birth, infant feeding and childhood hospitalization with infection

INTRODUCTION: Infections are a leading cause of mortality and morbidity in preschool children. We aimed to assess the impact of the co-occurrence of cesarean section, early birth and formula feeding on hospitalization with infection in early childhood. MATERIAL AND METHODS: Population-based retrospective record-linkage cohort study of 488 603 singleton livebirths ≥32 weeks' gestational age in New South Wales, Australia, 2007-2012. Multivariable Cox-regression was used to estimate independent and combined adjusted associations of gestational age, mode of birth (vaginal or cesarean section by labor onset) and formula feeding with time to first and repeat hospitalization with infection for children less than five years of age. RESULTS: In all, 95 346 (19.5%) children were hospitalized with infection, and of these 24.8% (23 615) more than once. Median age at first and repeat hospitalization was 1.1 and 1.7 years, respectively. Earlier gestation, modes of birth other than spontaneous vaginal, and formula feeding were independently associated with an increased risk of first and repeat hospitalization with infection. At 32-36 weeks' gestation, co-occurrence of perinatal factors (cf. spontaneous vaginal birth at 39+ weeks without formula feeding) was associated with a 2-fold and 1.5-fold increased risk of first and repeat hospitalization, respectively. For births at 37-38 weeks, the increased risk was 1.5-fold and 1.25-fold for first and repeat hospitalization, respectively. CONCLUSIONS: Cesarean section, labor induction, birth at