Pre-pregnancy body mass index, gestational weight gain and postnatal growth in preterm infants.

OBJECTIVE: To evaluate associations between pre-pregnancy body mass index (BMI), gestational weight gain (GWG), and postnatal growth in preterm infants.

DESIGN: A cohort study of 14,962 births < 32 weeks' gestation. We used multivariable linear regression to assess associations between maternal BMI or GWG (models stratified by BMI) and infant postnatal growth, defined as the difference between discharge and birth weight Z-scores based on Fenton or INTERGROWTH-21st growth charts.

RESULT: For BMI, obesity class 2 was positively associated with postnatal growth using the Fenton chart. Using INTERGROWTH-21st, inadequate or excessive GWG in women with underweight or obesity class 3 were associated with postnatal growth in different directions. Excessive GWG in women with normal weight was negatively associated with postnatal growth defined by Fenton.

CONCLUSION: Some categories of BMI and GWG were modestly associated with postnatal growth in preterm infants. Results were inconsistent within and between the INTERGROWTH-21st standard and Fenton growth reference.