Tests have shown that microwaves emit harmful electromagnetic radiation which could harm embryos and could lead to miscarriage.

"Microwaves can be harmful if they are leaking radiation," says Dr Shivani Sachdev Gaur of Phoenix hospital.

The waves of a microwave oven can travel up to 12 cm, so it is harmful for a pregnant woman to stand near a microwave oven, especially if it is old and damaged, she says.

If the door of the oven is damaged or if the user uses it with the door opened, then the leakage is more. In old microwave ovens the leakage levels of radiation could be more.

A survey conducted among Professional Service Associates, a group of US microwave repair servicemen, indicated that over 56 per cent microwave ovens two years or older leaked levels of radiation 10 per cent higher than the safety standards set by the FDA.

According to Dr Shaktibhan Khanna of Apollo Hospital, though no concrete study has come up on the ill-effects of microwaves, it is always advisable to take precautions.

"As of now, however, we are not asking women to avoid using the microwave during pregnancy," she says.

Microwave radiation is odourless and invisible and therefore hard to detect. Thus for those who work in or stay in areas designated for the use of radioactive materials, it is desirable that one should understand the biological risks of radiation to the unborn child.

Food is cooked in the microwave oven by exposing the food to microwave energy. Most of the household ovens operate at the frequency of 2,450 MHz that is 2,450 million cycles per second.

The magnetic tube in the oven converts the 60 Hz electric current to 2,450 Mhz of EMR. This is transferred to the oven easily through the wave guide, and then a mode stirrer spreads this energy evenly all over the oven cavity.