Infant's growth through the first year of life and maternal pre-pregnancy body mass index

Introduction: Despite its potential clinical relevance, association between maternal pre-pregnancy Body Mass Index (BMI)and infant's growth has been poorly investigated. Objectives: To assess whether an association may exist between maternal pregnancy BMI and infant's growth throughout the first year of life. Method/Design: Prospective observational cohort study including 1246 at term, singleton, healthy newborns. Mothers were interviewed before discharge about pre-pregnancy weight, sociodemographic data, lifestyle and were given a diary to record the type of feeding during the study period. Maternal pre-pregnancy BMI was categorized according to the World Health Organization criteria as: underweight (BMI<18,5kg/m2), normal-weight (18,5kg/m2<BMI<25kg/m2) and overweight (BMI>25kg/m2). Infant's growth (weight,lenght,BMI) data were collected during visits scheduled at 1,3,6,9,12 months of life, and z-scores were calculated. Results: Birth weight was lower in infants born to underweight (mean 3289g, SD 384) than normal-weight (mean 3416 g, SD 408) and overweight mothers (mean 3426 g, SD 431) (p<0,05). Throughout the first year of life, the infant's BMI z-score ranged between o,37 and 0,77 in the whole sample but was significantly higher in infants born to overweight than underweight and normal-weight mothers from 6 months onwards (maximum p=0,024). Significance of difference decreased (p=0,072) after adjusting for confounders (breastfeeding, solid foods introduction and type, mother age, educational level. No overall significant difference occured among underweight, normal-weight and overweight mothers for lenght z-score. Conclusions: The infant's BMI z-score pattern throughout the first year of life may be associated with maternal pre-pregnancy BMI.