I am not an obstetrician but I have never read of any negative health effects due to metal detectors.

Metal detectors *do not* emit any type of radiation. They operate by use of an electromagnetic field. The hand held ones work on exactly the same principal as the walk through ones. If you believe that this is injuring your baby then you should also not walk through any retail stores / libraries that use electromagnetic security tags.

There is a visual walk through x-ray system that I have heard about but I have never encountered it. See http://www.rapiscan.com/secure1000.html

Keba