The relationship of mammary temperature to parturition in human subjects

Four hundred and seventy thermography studies were performed on 210 women to measure mammary temperature prior to, during, and immediately following pregnancy. Mean mammary temperature of 33.3 +/- 0.1 degrees C. (S.E.M.) obtained in 14 nonpregnant patients increased to 34.2 +/- 0.1 C. (S.E.M.) by nine weeks of gestation (p less than 0.01). The difference between mammary and sternal temperature was negative in the nonpregnant state and became positive after 18 weeks of pregnancy. Mammary temperature remained significantly higher in the pregnant group than in the nonpregnant group (p less than 0.001) up to term. In six postpartum patients, a further increase from prepartum values to 35.4 +/- 0.6 degrees C. (S.E.M.) occurred. The results suggest that relatively large changes in mammary blood flow and/or metabolic rate take place in human subjects in early pregnancy and on the day following parturition.