Continuous monitoring of fetal temperature by noninvasive probe and its relationship to maternal temperature, fetal heart rate, and cord arterial oxygen and pH.

The human fetus is normally warmer than its mother. The principal route of fetal heat dissipation is through the placental circulation. We developed a technique that is noninvasive to the fetus to record the fetal skin and maternal uterine wall temperatures, from which we derived the temperature difference. We have established a range of normal values (mean temperature difference 0.24C) and present some preliminary data. The results show a correlation between changing temperature and baseline fetal heart rate (r = 0.628, P less than .001) and the influence of contractions and epidural analgesia on these measurements. Measurement of the fetal-maternal temperature difference during labor may help detect abnormal umbilical-placental blood flow, resulting in fetal distress, and may help distinguish sinister from iatrogenic fetal tachycardias. Our technique provides the first simple means of recording this basic fetal variable.