382 The Effect of Intrauterine Growth Restriction on Circulating Concentrations of Bone Collagen Markers in Full-Term Pregnancies

Abstract

Background and aims: Intrauterine-growthrestriction (IUGR) is associated with impaired fetal skeletal development. We aimed to investigate the effect of IUGR on bone turnover in mother/infant pairs, by determining circulating bone markers of type I collagen in full-term IUGR and appropriatefor- gestational-age-(AGA) pregnancies. Methods: Circulating markers of bone formation (carboxy-terminal propeptide of type I procollagen- PICP) and resorption (cross-linked telopeptide of type I collagen-ICTP) were measured by EIA and RIA, respectively, in 40 mothers and their 20 asymmetric IUGR and 20 AGA full-term fetuses and neonates on postnatal day 1-(N1) and 4-(N4). Results: Fetal PICP, as well as fetal and N4 ICTP concentrations were higher in the IUGR group (p=0.036, p=0.038 and p< 0.001, respectively). In both groups, maternal PICP and ICTP concentrations were lower than fetal, N1 and N4 ones (p< 0.001 in each case). In a combined group, N4 PICP concentrations were elevated compared to N1 ones (p=0.012). Fetal ICTP concentrations were higher in females (p=0.008). Conclusions: Type I collagen synthesis and degradation are higher in IUGR fetuses/neonates. Thus, we may speculate that IUGR may affect bone mineral density and bone protein matrix in opposite directions. Higher fetal/neonatal PICP and ICTP concentrations, as compared to maternal ones, may be attributed to the high rate of skeletal growth in the former. The postnatal rapid increase in bone metabolism may account for the gradual elevation in PICP concentrations during the first days of life. Finally, the higher fetal ICTP concentrations in females may be explained by gender-related differences in bone mass.