Intrauterine Blood Flow and Postnatal Development

An increasing number of long-term follow-up studies of growth-restricted infants has been published during the recent years. This chapter reviews implications of abnormal fetal blood flow in fetal growth restriction (FGR) on postnatal development. The majority of follow-up studies has focused on examining relationships between absent or reverse end-diastolic flow in the umbilical artery or the fetal descending aorta and the outcome. Early-onset FGR with severe fetal hemodynamic impairment resulting in very preterm birth is associated with increased perinatal mortality and has a modifying effect on several neonatal morbidities, e.g., cerebral intraventricular hemorrhage and necrotizing enterocolitis. It also appears to increase the risk for long-term cognitive impairment. Several studies have highlighted the challenge of differentiating the effects from early FGR to those of complications from very preterm birth. Late-onset FGR with abnormal umbilical/aortal blood flow has consistently been associated with an increased risk for minor neurological dysfunction and behavioral impairment. Evaluation with brain magnetic resonance imaging has indicated reduced regional volumes and altered tissue characteristics in FGR. These findings are in agreement with the report on decreased neuroretinal rim area in the ocular fundus as a measure of the optic nerve tissue in young adults with FGR and abnormal intrauterine blood flow. Redistribution of fetal blood flow with preferential supply of brain (brain sparing), diagnosed as a decreased pulsatility index (PI) in middle cerebral artery or decreased cerebroplacental PI ratio, has repeatedly been associated with deviations in neurodevelopment. Several studies have demonstrated that the redistribution of blood flow in the growth-restricted fetus, although beneficial for the intrauterine survival, may have long-lasting negative effects on cardiovascular function and growth. Those observations are in accord with the hypothesis of developmental origin of cardiovascular diseases in adult life, originally based on epidemiological studies. Short- and long-term studies in subjects with FGR and abnormal intrauterine blood flow have observed reduced vascular growth, increased pulse pressure, indications of altered endothelial function, and cardiac morphological changes. Doppler ultrasound evaluation of fetal hemodynamics has increased our understanding of the physiological mechanisms involved in FGR and the follow-up studies in subjects with abnormal fetal blood flow have given valuable information on effects of FGR on postnatal development. This new knowledge underlines the importance of routine follow-up of infants with FGR in order to optimize their postnatal development by potentially offering preventive measures and by early diagnosing deviations from normal development.