Natan Haratz-Rubinstein ob-gyn
"Radiation" is a terrifying word to expectant mothers, so you'll be glad to hear that plane travel is generally safe in this regard.
Whether we're on land or in the air, we're exposed every day to cosmic ionizing radiation, which emanates from the sun and other stars. On the ground, the Earth's atmosphere offers some protection from the radiation. At high altitudes, the air is thinner and radiation levels are somewhat higher, but they're not usually high enough to be of concern to the occasional traveler.
Radiation levels can be a lot higher, though, during solar flares — bursts of electromagnetic radiation caused by disturbances in the sun's atmosphere. Fortunately, solar flares are rare and last only a short while.
The National Oceanic and Atmospheric Administration posts solar radiation storm alerts on its Web site. Some experts recommend that pregnant women check the site before flying and consider postponing their trip a day or two if a storm is forecast.
Some experts think that cosmic radiation could pose a small risk to flight crews and frequent fliers, and there is ongoing research to assess these risks. In some countries, pregnant crew members are reassigned to low-altitude flights or given jobs on the ground for the duration of their pregnancies. But for infrequent air travelers, pregnant or not, the risk from cosmic ionizing radiation under normal solar conditions is considered negligible.