Antibiotic exposure and growth patterns in preterm, very low birth weight infants.

Background: Antibiotic exposure in term infants has been associated with later obesity. Premature, very-low-birth-weight (birth weight ≤ 1500 g) infants in the neonatal intensive care unit frequently are exposed to antibiotics. Our hypothesis was that in preterm infants, there is a positive linear and dose-dependent relationship between antibiotic exposure and growth from birth through 12 months' corrected age.

Methods: Retrospective analysis of prospectively collected data of all antibiotic use among inborn, preterm (≤32 weeks' gestation), very-low-birth-weight infants admitted to the neonatal intensive care unit at Parkland Memorial Hospital and followed in the Low Birth Weight Clinic at Children's Medical Center, Dallas, TX. Antibiotic use was quantified by days of therapy which was compared with weight and length parameters at birth, 36 weeks' postmenstrual age, and 2, 4, 6, and 12 months' corrected age. The change in weight and length z-scores from birth to all subsequent age points was calculated. Stepwise multivariate regression analysis was performed to determine predictors of weight, length, and weight-for-length delta z-scores from birth to each subsequent age point.

Results: During the 18-month study, 161 infants received a median of 11 (IQR, 5.5-19.5) antibiotic days of therapy which was not associated with weight or length delta z-scores from birth through 12 months' corrected age.

Conclusion: Association of prolonged antibiotic use and neonatal morbidities and mortality may override the potential association with increased weight gain in the NICU and beyond.