Fetal growth restriction: pathogenic mechanisms.

Complex genetic and environmental mechanisms of maternal, fetal and placental origin regulate fetal growth and may contribute to fetal growth restriction (FGR). The somatotrophic regulatory factors include IGF-I, IGF-II, the IGF binding proteins (IGFBP) 1-6, IGF receptors 1 and 2, and the IGFBP specific proteases. Abnormal remodeling of utero-placental arteries and abnormal fetal-placental angiogenesis has also been implicated in FGR. The underlying molecular mediators include vascular endothelial growth factor (VEGF), placental growth factor (PlGF), VEGF receptors, VEGF binding proteins, and numerous other agents working through multiple pathways many of which still remain unknown. Expression of these major angiogenic factors appears to be regulated by local oxygen partial pressure. Future investigations may resolve many of these issues not only adding to the clarity of our understanding of the mechanisms of growth restriction but also improving clinical management.