The Effects of Maternal Hypoxia and Hyperoxia Upon the Neonatal Pulmonary Vasculature

The fetal and newborn pulmonary artery has thickened media by comparison to that of the older infant. In this study we investigated the proposition that chronic maternal hypoxia during the latter part of gestation might induce further thickening of the neonatal pulmonary artery media. Relative medial thickness was determined by the ratio of the arterial media to external diameter. The mean ratio of small pulmonary arteries of progeny of hypoxic mothers was significantly thicker in each size group between 50 and 150 microns as compared to those born to mothers who spent their gestation in air or hyperoxic environments. Medial hypertrophy was most pronounced in the smaller arteries of the hypoxic group; no intersize variations were found between the control or hyperoxic groups. Medial thickness decreased in all arteries through 2 weeks of age; this decrease was greatest in control and hyperoxic arteries. The possible relationship of hypertrophied pulmonary arterial media and abnormally increased neonatal pulmonary vascular resistance is discussed.