Innate small babies are metabolically healthy children.

Abstract

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). 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). 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. 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). 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.