Placental circulation, fetal growth, and stiffness of the abdominal aorta in newborn infants.

Abstract

To measure the elastic properties of the abdominal aorta in normal infants and infants who had umbilical placental insufficiency (UPI) before birth. An index of aortic stiffness was measured in 65 infants who were appropriate-for-gestational age (32 preterm infants between 29 and 40 weeks of gestation) and 51 compromised infants who were identified antenatally by an umbilical artery Doppler flow waveform >95th percentile. An aortic stiffness index (SI) was measured with a phase-locked loop ultrasound technique to estimate the aortic systolic and diastolic diameters and their correlation with blood pressure. In normal infants, the aortic systolic and diastolic diameters, as well as the SI, increased with the gestational age. In the infants with UPI, aortic diameter and blood pressure were normal, but SI was increased. Infants from the compromised group with an SI >95th percentile for their gestational age had a significantly worse clinical outcome. The increase of afterload caused by UPI resulted in a decrease of aortic distensibility during the neonatal period, suggesting an alteration of aortic wall structure.