A scenario that sometimes happens, when somebody adopts a new female rat, is they adopt a rat that they didn't know or whoever adopted to them, didn't know that she was pregnant. And they may find, within a short period of time, that she's given birth.
In the majority of situations, she's able to deliver those babies without any problems and rat mothers are excellent mothers. They rarely have complications and they always take care of their young. They are willing to nurse them and raise them, even in sometimes the most, or the least ideal environment, they will raise their young fine.
In other situations, you may find a scenario, where you're left with babies, without a mother. Let's say, something happens to the mother, whose given birth. Or let's say, somebody finds a litter of baby rats and the mother is nowhere around. In this particular instance, the best thing to do, is seek out somebody who works with rats, somebody in a rat rescue organization, a veterinarian or animal care specialist that deals with this. And consult with them for some advice on, how you may attempt to try to raise them, should you choose to do so.
In other situations, a female rat that gives birth, doesn't require, the babies don't require any additional care, any special care or anything additional, leaving the mother to raise them, to take care of them. And then when they are weaned, proper handling and socialization are generally, all you need, in taking care of baby rats.