Those microwave things are great and probably safer than a heating pad anyway. It should be pretty safe for you but you may want to check with your doctor to be sure. Those Icy Hot patches might have a warning on the label to warn against the use during pregnancy.

When I was pregnant(both times), I had leg cramps/restless legs. It was maddening. It kept me awake. I think your Mom is right....all this is just an exercise in preparedness for the upcoming event