Perspective: growth factors in normal and abnormal fetal growth.

Growth factors (GFs) and growth inhibitors (GIs) are important regulators of cell proliferation and differentiation in many cell types. Insulin growth factor I and II, epidermal growth factor, transforming growth factor alpha and transforming growth factor beta are produced and secreted by various fetal tissues, and their cognate membrane receptors are present in the fetal-placental unit. These findings suggest that fetal growth and development are regulated by these or other GFs and GIs in an autocrine or paracrine manner. A well-coordinated and integrated action of several GFs/GIs may be operating in promoting the growth and development of different fetal organs during the various stages of gestation. An interruption of the coordinated pathway due to an abnormal expression of GFs/GIs, a structural aberration of their receptors, or an impairment in the postreceptor signaling mechanism may contribute to abnormal fetal growth. The investigation of the unique role of a single GF/GI, the integrated action of several of them in fetal growth, and the points of abnormalities in this mechanism in abnormal fetal growth have both fundamental and clinical relevance.