Temperature elevation in the foetus is of concern for excess heat load including that from radio frequency (RF) exposure. According to international guidelines, the temperature elevation in the foetus should be less than 0.5℃ for RF exposure from magnetic resonance (MR) equipment. However, no previous study has succeeded in simulating the temperature difference between the mother and foetus even in the thermoneutral condition. The present study develops a thermal model for a pregnant woman and then applies it to simulate the temperature variations in the pregnant woman due to ambient heat exposure and RF plane wave exposure. From the computational results with the thermal model, the foetal temperature in the thermoneutral condition was 37.5℃, which is 0.35℃ larger than that of the mother and coincides with the measured temperature. When the pregnant woman model is exposed to ambient temperature of 35.5℃, the core temperature elevations in the mother and the foetus are almost identical. On the contrary, the foetal temperature elevation for RF exposure is higher than that in the mother. This higher temperature elevation in the foetus becomes obvious, particularly when relative large electromagnetic energy absorption occurs in and around the foetus.
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