Okay, I think this one was made up by a pregnant woman to get out of cleaning the kitty litter.
I can't say I blame her, between morning sickness and an extra 30lbs, scooping out cat poo is about the last thing you want to do. But what if you're the only one around and your cat is standing on a mountain of crap?
The big scare on this one is something called toxoplasmosis. It's a parasite that is transmitted between warm blooded animals. You can get it from ingesting the raw or uncooked meat from something infected with it or from ingesting the feces of an infected cat. It can cause all kinds of nasty problems in an unborn child like brain damage and blindness, just to name a few.
The cat most likely got it from eating an infected rodent so if Mittens is an indoor cat, you're probably okay. Even if he does have it, you literally have to ingest the parasite (well technically a cyst called an oocyst) in his poop.
This one also sounds like a bit of a run away train because if you worry about the poop in the litter box, then you need to worry about the poop that may be in garden soil and if you don't garden well what about the person who was gardening and shook your hand and then you touched your mouth?! You see where this one is going.
It looks like this is a relatively rare thing and to it sounds like becoming infected when you're pregnant is a bit of a perfect storm but with the effects being so scary, it gets a lot of attention.
Hey, if you can get out of it, go for it. If you can't, a little hand washing or glove wearing will go along way, that, and maybe cutting down on your cat shit consumption – at least during your pregnancy anyway.
search: toxoplasmosis, cat litter during pregnancy, oocyst