I am all for women, and mostly for pregnancy. But I am also for, you know, quantitative science and the lowly photon. Here are some fun facts that we should all know.
The radiation dose you receive from full body scanners (0.005 - 0.01 mrem) is about ten thousand times less than want you experience on an annual basis just by living on Earth (360 mrem). Moreover it is 100 times less than your yearly dental x-rays (1 - 20 mrem). In fact, you will be subjected to a much higher radiation exposure on the plane flight itself than you receive by going through the scanner.
The real issue with these heinous machines is privacy, not safety (even to a fetus).