Amniotic fluid and fetal tissues are not heated by obstetric ultrasound scanning

Amniotic fluid temperature in first trimester pregnancies and fetal subcutaneous tissue and amniotic fluid temperature in second trimester pregnancies, measured by a thermocouple probe, did not increase during sector, linear-array or Doppler ultrasound scanning. The mean fetal muscle temperature was higher (36.9 degrees C) than mean amniotic fluid temperature (36.6 degrees C) during the second trimester.