Study of preterm infants' gut microbiome and its relationship to BMI at childhood. Postnatal Gut Microbiome Development Influenced Early Childhood Growth In Preterm

Background: Preterm infants are at high risk for growth deficit due to the disruption of normal intrauterine growth and nutrition. Early nutritional support and catch-up growth can play an important role in childhood health and obesity prevention. Our study examined the relationship between the timing of catch-up growth in preterm infants and their childhood body mass index (BMI). Methods: This is a retrospective study of infants who were born <35 weeks between 2012-2018 and had at least one well visit during 2-5 years of age. Weight and length z-scores at birth, 1, 2, 4, 6, 12 and 15 months, and BMI and length z-scores from 2 to 5 years of age were collected. Catch up growths were calculated by changes in z-scores and divided into early period of 0-4 months and late period of 4-18 months. NICU nutritional data including maximum caloric concentration (kcal/oz) and daily intake (kcal/kg/day), and macronutrient supplementation such as protein and medium chain triglycerides were also collected. Results: There were 160 infants included in the final analysis with birth weight and gestational age of 1149 ± 496 grams and 28 ± 3 weeks. The maximum caloric concentration and daily intake were 25 ± 2 kcal/oz and 130 ± 14 kcal/kg/day. Macronutrient supplementation was given in 66 (41%) out of 160 infants and not associated with childhood BMI. Results suggested that the late (4 -18 months) as well as the early (birth - 4 months) catch up growth in weight positively correlated with childhood BMI. The length z-scores at 2 years correlated positively with early and negatively with late catch up growths in weight. Conclusion: Our findings suggest that optimal NICU nutrition to promote early catch up growth in weight improved linear growth without having an association with increase in childhood BMI. Childhood body mass index is influenced by catch up growth during infancy.