Reference Ranges of Blood Flow in the Major Vessels of the Normal Human Fetal Circulation at Term by Phase-Contrast Magnetic Resonance Imaging

Abstract

Background-Phase-contrast MRI with metric-optimized gating is a promising new technique for studying the distribution of the fetal circulation. However, mean and reference ranges for blood flow measurements made in the major fetal vessels using this technique are yet to be established. , 29 (7, 51). A strong inverse relationship between foramen ovale shunt and pulmonary blood flow was noted (r=−0.64; P<0.0001). Conclusions-Although too small a sample size to provide normal ranges, these results are in keeping with those predicted in humans based on measurements made in fetal lambs using radioactive microspheres and provide preliminary reference ranges for the late-gestation human fetuses. The wide range we found in foramen ovale shunting suggests a degree of variability in the way blood is streamed through the fetal circulation. (Circ Cardiovasc Imaging. 2014;7:663-670.)

Neurodevelopmental Outcomes in Children With Congenital Heart Disease—What Can We Impact?

“…When significant structural disease exists within the heart, these beneficial patterns are likely to be altered. Recently confirmed by fetal magnetic resonance T-2 relaxation measurements, fetuses with transposition of the great arteries have the blood with the lowest saturation of oxygen returning to the ascending aorta and brain, while blood with the highest saturation returns to the abdominal organs and placenta (17, 19). Speculation on the consequences of the transposed fetal circulation (as an explanation for the high incidence of macrosomia in these infants) dates back nearly 50 years and has also been offered as an explanation for the increased incidence of relative microcephaly and long-term developmental challenges seen so often in transposition of the great arteries (20).…”

Better timing for cord clamping is after onset of lung aeration

“…In human fetuses, a strong inverse relationship exists between foramen ovale shunt and pulmonary venous return (3). The foramen ovale shunt is primarily dependent on umbilical venous return while pulmonary venous return is the second source of left ventricular preload.…”

Fetal Physiology and the Transition to Extrauterine Life

“…The development of the pulmonary circulation starts by 34 days’ gestation in the human fetus. Advances in fetal magnetic resonance imaging (MRI) have allowed more precise examination of the relative blood flow in the human fetus, and recent evidence suggests that pulmonary blood flow increases with gestational age from an initial low of 10% to almost 50% of the combined ventricular output by term gestation 14 .…”