To the Editor. —
I read with interest the timely and informative article on pregnancy and travel by Drs Barry and Bia.1 However, a common error was made in explaining the effects of high altitude exposure of the mother on fetal oxygenation. The oxygen tension values for umbilical artery and vein were reversed. Umbilical venous blood, which is returning from the placenta, has the highest oxygen content in the fetus, with a PO2 of 32 mm Hg. In a sense, the umbilical vein is similar to the pulmonary vein in the adult circulation. This better oxygenated blood flows preferentially to the ascending aorta (via right atrium, foramen ovale, and left atrium), allowing greater oxygen delivery to the fetal heart and brain. Blood in the descending aorta comes from systemic venous return to the right side of the heart (via pulmonary artery and ductus arteriosus) and has a much
Mannino FL. Pregnancy and Travel: The Risks of Hepatitis and Scuba Diving. JAMA. 1989;262(4):497. doi:10.1001/jama.1989.03430040067014
Customize your JAMA Network experience by selecting one or more topics from the list below.