From the Departments of Obstetrics and Pediatrics, University of Cincinnati College of Medicine and the Cincinnati General Hospital, the Laboratory for the Study of Infant and Maternal Health, and the Children's Hospital Research Foundation, Cincinnati, Ohio.

The authors wish to thank the following for their help and interest in furnishing data on patients: Drs. Virginia Apgar, Meyer Halperin, J. R. Herron, L. S. James, F. Leake, George F. Paine, Paul Rahter, J. V. Siller, and S. N. Surks.