Methods

In an initial series of observations, 24 healthy full-term infants from the obstetric service of the Sloane Hospital were studied. The infants were divided into two groups," warm" and" cool." Each of these two groups consisted of six infants delivered by elective Cesarean section and six delivered vaginally. The two groups were considered comparable in regard to premedication, anesthesia, birth weight, and Apgar score 1 (3) at 1 minute (see Table I). All vaginal deliveries were uncomplicated, being either spontaneous or by low forceps.

The environment to which a particular infant was assigned was determined before delivery by a random permutation of numbers in groups of four. The period of observation was continued for approximately 2 hours from the time of birth. In the warm group deep rectal temperature was maintained at approximately 37.00 C by placing the infant immediately after birth under a thermostatically controlled radiant heating device. 2 They were left exposed to the radiant heat ex-cept when draping was necessary for obtaining blood samples. Infants in the" cool" group were left un-covered at room temperature (mean, 25.00 C; range, 22.5 to 26.5 C). Temperatures in all infants were monitored continuously by thermistor probes and a multichannel polygraph. Thermistors were placed in the rectum (8 cm from anus), on the skin of the anterior abdominal wall, and in the room air. In the warm group the skin thermistor was shielded from the direct heating of the infrared lamp.