Context: Birth weight (BW) is usually taken as a surrogate of fetal growth. However, BW per se is not relevant enough in assessing fetal growth restriction, which by itself may alter body composition, metabolic, and hormonal profiles at birth (irrespective of BW), reflecting the necessary adaptive changes in metabolism under poor fetal environment.
Objective: Our objective was to measure body composition, hormonal, and metabolic parameters at birth in relation to both BW and fetal growth velocity.
Methods: A total of 235 pregnancies at risk of low BW were included, and newborns were observed at birth. Fetal growth velocity was calculated as the change in customized percentiles of estimated fetal weight between 22 wk gestational age and birth. Newborns were ranked in descending order of fetal growth velocity and divided in three equal tertiles.
Results: The lower fetal growth velocity tertile showed a severe fetal growth restriction (-52% +/- 21%) and was significantly associated with reduced lean and fat mass (P < 0.001 and 0.02, respectively). Insulin concentration was significantly related to fetal growth velocity (P = 0.006) and fat mass (P = 004) but not to BW (grams), whereas fetal growth velocity (P = 0.002) and BW (P < 0.001) but not fat mass had a significant effect on IGF-I concentration at birth.
Conclusion: Fetal growth restriction induces changes in body composition and metabolism suggestive of a higher insulin sensitivity independently from BW itself, reflecting adaptive changes to an adverse fetal nutritional environment.