Cardiac Malformations in the Rat Induced by Maternal Hypercapnia with Hypoxia

Abstract

Forty-seven pregnant rats were exposed for 24 hours to a gas mixture of 6% carbon dioxide, 10% oxygen and 84% nitrogen on different days during gestation. The earliest exposure was on the fifth day after observed copulation, the latest on the sixteenth. The hearts of 370 newborn test rats were studied in serial sections and compared with those from 111 newborn control rats. The over-all incidence of cardiac malformations was 28.1% in the experimental animals and 4.5 % in the controls. In the test groups, severe structural anomalies resulted from exposures as early as the fifth day of gestation.

The results of the present and of previous experiments suggest that maternal hypercapnia in the presence of normal and low oxygen tensions is markedly teratogenic for the cardiovascular system in the rat.