Identification of newborns with Fetal Growth Restriction (FGR) in weight and/or length based on constitutional growth potential

This study was carried out to build statistical models for defining FGR (Fetal Growth Restriction) in weight and/or length after taking growth potential of an infant into account. From a cohort of pregnant women having given birth to 47,733 infants in 141 French maternity units, two statistical models gave individualized limits of birth weight and birth length (based on the 5th centile) below which, after adjustment for its individual growth potential, a newborn must be considered as FGR in weight and/or in length. A sample of 906 infants had measures taken of cord blood growth factors (IGF1, IGFBP3). The FGR_W definition (weight<5th centile for growth potential) permitted the identification of infants who presented rates of maternal hypertension (13.6%) and of Apgar score at 5 min<6 (2.9%) higher than in the classical group SGA_W (weight<5th centile for sex and gestational age) (9.6% and 2.2% respectively). By combining FGR_W and SGA_W, a subgroup of infants, not currently recognized as SGA, presented very high rates of maternal hypertension (19.9%) and of low Apgar score (3.9%). Conversely a subgroup of infants, currently recognized as SGA_W, had rates as low as in the normal infants group, and had to be considered as “constitutionally small” (that is to say 24% of the SGA_W). Combining FGR_W and FGR_L (length<5th centile of growth potential), 7.6% of infants appeared growth-restricted, and 1.8% appeared constitutionally small in weight and/or in length. The FGR_W–FGR_L infants showed the lowest mean values of IGF1 (126.2±3.2) and IGFBP3 (0.86±0.03). These new definitions of FGR_W and FGR_L could help to better identify infants at birth requiring neonatal care, and monitoring of growth catch-up and neurodevelopmental outcome.