Nitrous Oxide in Early Labor  Safety and Analgesic Efficacy Assessed by a Double-blind, Placebo-controlled Study

*Research Associate, Department of Anesthesia, The Toronto Hospital.

†Research Fellow, Department of Anesthesia, The Toronto Hospital.

‡Assistant Professor, Department of Anesthesia, The Toronto Hospital.

‡Assistant Professor, Department of Anesthesia, The Toronto Hospital.

§Medical Research Council of Canada Scholar, Department of Psychology, The Toronto Hospital, Toronto General Division; Assistant Professor, Departments of Behavioral Science and Anaesthesia, University of Toronto.

‖Associate Professor, Department of Anesthesia, University of Toronto; Anesthetist-in-Chief, The Toronto Hospital.