Q: I have read some things telling me that flying while pregnant is okay and some other things that say I should worry about an increased risk of radiation or cancer for my children if I do fly while I'm pregnant. Can you clarify this?

A: The background risks for birth defects in all pregnancies are about 3% and for miscarriage they are 15-25%; this is the normal incidence. The most important factor with regard to radiation risks is the dose. Fortunately, when you are flying in a jet at 30,000 feet altitude the exposure is extremely small and for only a short period.

Based on our knowledge of the amount of radiation to result in birth defects or miscarriage, there is no risk from commercial flying. The reason why consultants differ in their statements on the risk of childhood cancer is that there is a theoretical risk of cancer from any exposure of radiation (ionizing). But when the dose is as low as it is when you are flying, the theoretical risk is dwarfed by the spontaneous risk of cancer. So you could say the cancer risk from flying is very, very, very, small or you could say it should be of no concern because the dose is so low.