Perinatal predictors of growth at six months in small for gestational age babies.

Abstract

Poor growth in childhood is associated with a number of later complications and early recognition may enable early intervention to improve outcomes. Approximately 20% of small for gestational age (SGA) babies remain small at two years. Most catch up growth occurs in the first 6 months and smallness at 6 months predicts later small size in the majority of cases. There are no previous reports of perinatal predictors of size at 6 months in SGA babies. The aim of this study was to identify the perinatal factors associated with small size at 6 months in infants who were SGA at birth (birthweight < 10th%). SGA infants had assessments of length, weight, and head circumference performed at three monthly intervals by the same researcher. Detailed perinatal data was collected in all cases. Abnormal size was defined as a length, weight or head circumference measurement < 10th% for 6 months corrected age. Infants were considered to show failure of catch-up growth if measurements at 6 months were further below the population mean than birth measurements. Two hundred and forty eight babies were recruited of whom 203 (82%) completed followup at 6 months. Forty (20%) babies were short, and in logistic regression shortness at 6 months was predicted by shortness at birth and male sex. Thirty one (16%) had weight < 10th% and low weight was predicted in logistic regression by early gestation at diagnosis of SGA (median 30.8 weeks in those who were under weight and 33.9 weeks in those of normal weight p < 0.0001). Thirty seven (18%) had a low head circumference which was predicted by small head size at birth. Three quarters of the babies who were short, underweight, or had low head circumference at 6 months also showed failure of catch-up growth. Shortness and small head circumference at 6 months were predicted by shortness and small head circumference at birth, especially in boys. Underweight was predicted by early detection of SGA antenatally. Most SGA babies who remained small at 6 months failed to show catch up growth after birth.