You know what I don't understand? Even if the risk of LCM was legitimate, there is TESTING to see if your rodents have it or have been recently exposed.. it's not cheap to do, but it's not extremely expensive either... and no one has mentioned it?
When I had rats I had them tested regularly through RADIL in Missouri.. mostly for peace of mind any time I brought a new one (or a group) in, but also to make sure I hadn't unwittingly exposed them to anything (a lot of rat diseases can be spread by human contact - from pet stores, etc). (broken link removed) covers the tests that are important and it's only $39, but it usually costs a bit more to get the sample drawn and shipped to the lab.
If you are concerned to the point of re-homing your pets based on a "maybe" situation, at least do the right thing and TEST them to know for sure if you need to worry or not.
So put me solidly in the "inexcusable" camp in regards to getting rid of one's pets based only on fear and not actual information. I had rats all the way through my first two pregnancies and part of my third, and I experienced no problems, and neither did my kids, and I didn't rehome my rats. I chose not to add any more after my 2nd kid was born, and I did place a few with friends... but that was for other reasons than pregnancy, and I still had the remainder of my rats for almost another 2 years.