Is It Safe To Fly Frequently? For pregnant women, the maximum
exposure limit is 1 mSv over a 40-week pregnancy. In Europe the
1 mSv guideline is the law, but it is only advisory in the US.
While the exact threshold isn't certain, radiation exposure to
the unborn baby may increase the risk of developing cancer, such
as leukemia, during childhood. At airline altitudes, cosmic
radiation levels are greater than at sea level because the
earth's atmosphere absorbs much of the radiation before it
reaches the ground. The magnitude of in-flight exposure depends
strongly on altitude. For instance, the radiation dose received
on a short, low-altitude flight between two US states would be
far lower than a long, inter- or intra-continental flight at
high altitude. A round-trip flight between New York and Tokyo
would amount to 15 percent of the maximum exposure allowed
(1mSv), whereas a round-trip flight from New York to Seattle
would deliver 6 percent of the limit. According to the
commentary, physicians can assure pregna