The Effect of Morbidity and Sex on Postnatal Growth of Very Preterm Infants: A Multicenter Cohort Study

Background: Extrauterine growth restriction is common in the preterm infant, and it is associated with poor neurodevelopment. Nutrition plays an important role in postnatal growth, but growth is also influenced by other factors like co-morbidity, and, also, there might be sex differences. Methods: This is a cohort study including preterm infants < 32 weeks at birth (n = 21,825) from the Spanish Neonatal Network database. The effect of sex and morbidity (patent ductus arteriosus, bronchopulmonary dysplasia, necrotizing enterocolitis and late-onset sepsis) on weight gain as well as linear and head growth from birth to discharge/death was assessed with linear regression models adjusted by gestational age and Z-scores at birth. Results: The 4 selected morbidities had an independent effect on all 6 growth parameters studied, which was greater in the case of necrotizing enterocolitis: changes in weight, length and head Z-scores were –0.60 (95% CI: –0.66 to –0.55), –0.62 (95% CI: –0.70 to –0.54) and –0.63 (95% CI: –0.71 to –0.56), respectively. Weight gain and linear growth were overall more affected than head growth. Girls lost slightly more weight Z-scores (–0.03; 95% CI: –0.06 to –0.002) than boys after adjustment by morbidity. There were no significant gender differences regarding linear and head growth velocity (cm/week), although girls lost more head Z-scores (–0.14; 95% CI: –0.18 to –0.10). Conclusions: Main co-morbidities associated with prematurity have an impact on postnatal growth. Head growth is less affected than length and weight. Girls are at slightly higher risk of postnatal weight and head restriction after adjustment by morbidity.