P40.01: Multislice display of the fetal face using 3D ultrasound

Abstract

The test for pulmonary vascular reactivity in the fetus compares changes in branch pulmonary artery Doppler flow patterns with the mother breathing room air with maternal hyperoxygenation. A normal response to oxygen is to increase the pulmonary flow patterns and is seen in fetuses greater than 30 weeks’ gestation. Fetuses with severe growth restriction have redistribution of cardiac output to the brain, coronary and adrenal circulations. In fetuses greater than 30 weeks’ gestation with absent or reversed diastolic flow in the free loop of the umbilical artery and increased diastolic flow in the middle cerebral artery, the pulsatility of the flow in the branch pulmonary artery did not change with maternal hyperoxygenation. This indicates a fixed pulmonary vasoconstriction similar to what is seen in fetuses with pulmonary hypoplasia, yet these fetuses had normal respiratory function for gestational age after delivery. In fifteen fetuses hospitalized for growth less than 10% of prediction for age with abnormal umbilical artery Doppler flow patterns, the hyperoxygenation test was offered to mothers after obtaining consent. The results from these studies were compared to 15 fetuses whose mothers were hospitalized for pre-eclampsia, premature rupture of the membranes and abruption. Those fetuses whose growth biometry was within normal limits had normal pulmonary vascular response to the maternal hyperoxygenation test while those with severe growth restriction did not. Of those fetuses who had received antenatal steroids prior to the hyperoxygenation test, there was no effect on pulmonary vasodilatation in those with severe growth restriction but those fetuses with normal growth appeared to have an exaggerated positive response.