Innate Small Babies Are Metabolically Healthy Children

BACKGROUND: Being born small for gestational age (SGA) is regarded as a risk factor for later metabolic complications. The SGA is defined as a birth weight below -2 SD of the distribution for sex and gestational age. However, the definition of SGA does not distinguish between those born after fetal growth restriction and innate SGA (iSGA). OBJECTIVE: Our objective was to test whether innate SGA infants show any metabolic complications at the age of 2 yr in comparison with infants born appropriate for gestational age (AGA). METHODS: Fifty-eight infants with family SGA risk factors (SGA in a previous pregnancy or among parents, maternal height less than -2 sd for adult height in French women, and small fetal size at second-trimester ultrasound examination) were prospectively followed from midgestation to 2 yr of age. Fetal growth velocity was measured from ultrasound measurements. Body composition and hormonal profile were measured at birth and 1 and 2 yr. RESULTS: Fetal growth velocity was not significantly different between iSGA and AGA (-0.17 ± 0.2 vs. -0.17 ± 0.3 percentiles/d of gestation; P = 0.96). iSGA infants were significantly lighter at birth (-1.7 ± 0.45 vs. 0.46 ± 0.77 SD; P < 0.0001) and at 4 months of age (-0.85 ± 0.88 vs. 0.29 ± 1 SD; P < 0.0001), and they remain so over follow-up (-0.73 ± 1.08 vs. 0.2 ± 1.02 SD; P = 0.0014 at 2 yr). Height z-scores and percent fat time courses followed a similar pattern. No differences in any of the metabolic and hormonal parameters were observed between iSGA and AGA up to 2 yr (insulin at birth, 5.1 ± 6.8 vs. 5.2 ± 4.6 mIU/liter, P = 0.2; at 2 yr, 2 ± 1.6 vs. 2 ± 1.5 mIU/liter, P = 0.66). CONCLUSION: Infants born iSGA do not experience severe fetal growth restriction and do not show any evidence of metabolic risk either at birth or in the first 2 yr of life.