I've never actually done this. . but everything I read says not to do it because it can cause hot spots. If you shake the bottles when you're done nuking them wouldn't the hotspots go away?
I'm lucky b/c my kid is not picky and will even take a bottle cold; I'm just wondering if that was the only reason why you shouldn't or if there was something more substantial as well.
Re: About microwaving formula.
I mix on demand these days b/c we're using drop ins, but I used to premix and micro. Never had a problem. And both the pedi and the baby book I have said it was fine--do it for short periods of time and shake well. Test on wrist before feeding. No problem. Just don't micro BM b/c it changes the nutrative values.
Any time you heat BM to a temperature that is too high, the antibodies will be damaged. It really doesn't matter if it's a bottle warmer, the microwave or a pan of hot water. It's my understanding that heating is ok and the antibodies will stay intact if you do not get it too hot. Honestly, when heated in the microwave with the glass of water, the bottle turns out cooler than when I use the bottle warmer.