Association of birth weight centiles with infant and child growth dynamics

ImportanceInfants born small or large for gestational age exhibit different growth patterns compared with appropriate-for-gestational age counterparts. Evidence is lacking on how birth weight centiles beyond conventional thresholds predict early life growth. ObjectiveQuantify association of birth weight centile range with infant and child growth. DesignProspective cohort study. SettingFrance, Netherlands, Portugal, Singapore, United Kingdom, United States. ParticipantsSingletons from seven birth cohort studies with repeated growth measurements from age one week to 10 years. Five European cohorts were used for discovery analysis, and remaining cohorts for replication. ExposuresBirth weight centiles standardised for sex and gestational age using the INTERGROWTH-21st standards and classified into deciles. Main Outcomes and MeasuresInfant height (cm/month) and weight (g/month) velocity at 1, 6, 12, 24 months, body mass index (BMI: kg/m2) and age (months or years) at infancy BMI peak and childhood BMI rebound, and overweight/obesity at age 10 years. ResultsThe discovery analysis included 36,018 children (48% girls, birth years: 1991-2011). Growth velocity, peak BMI (mean: 17.7 vs. 17.3 kg/m2), age at peak BMI (10.2 vs. 10.4 months), rebound BMI (15.6 vs. 15.5 kg/m2), age at rebound BMI (5.3 vs. 5.0 years), and overweight/obesity prevalence were broadly similar in boys and girls. Compared with lowest birth weight decile (<10th centile), all higher decile groups had an initially lower height velocity that reversed by 24 months, an increasingly higher weight velocity through infancy, a higher and earlier peak BMI, higher rebound BMI, and a higher probability of overweight/obesity at age 10 years. For example, mean differences in BMI and age at peak BMI, and probability of overweight/obesity at age 10 years for the 7th (vs. 1st) birth weight decile were 0.77 kg/m2 (0.72 to 0.82), -0.58 months (-0.69 to -0.46), and 34% (18 to 49). Birth weight was not associated with age at rebound BMI. Replication analyses (n=2,517) supported findings. Associations were typically linear and consistent for boys and girls. Deciles provided only modest predictive gains over conventional categories. Conclusions and RelevanceBirth weight centiles may identify high-risk children missed by traditional thresholds, although predictive benefit over conventional groups was modest.