I remember I read an article before. It was about 米水 and milk. It said they are both good for babies if babies drink them separately, one is for vitamin A, the other is for vitamin B (sorry, I don't remember which one exactly for what :)
But if 粥水開奶, 粥水will destroy some nutrients in milk, so it is not suggested.
Also, it said babies can't get many nutrients from 煲湯, because the nutrients mostly have gone after cooking long long time.