Concerns have been raised regarding the use of electric blankets or other heating devices such as heating pads or heated water beds while pregant. There is little scientific evidence to prove one way or the other whether these devices may be harmful. There are two areas that should be looked at: electromagnetic fields and body temperature.
Some long-standing research data suggests that the extremely weak electromagnetic field generated by objects such as electric blankets are biologically harmless. Some studies contradict this claim, suggesting that these weak electromagnetic fields may contribute to changes in stress level, memory lapse, cancer, miscarriage or impaired fetal development. These studies, by their own admission, are inconclusive, as they cannot prove that cell damage in test tube experiments is replicated in actual human beings.
Another concern of using heating devices during pregnancy is the actual heat that these products generate. It is possible that raising your body temperature to 101 degrees or higher for an extended period of time may contribute to the risk of miscarriage or neural tube defects. However, It is highly unlikely that such a device would raise your body temperature this significantly or for an extended period of time.
If you are concerned, you should discuss the use of heating devices with your physician. She may have additional suggestions based on your own unique medical history.