A. What I think your granddaughter's Pediatrician really means is that she doesn't need any 'extra' water. You are right that everyone needs water or fluid to live, but a baby gets that already from her formula, or breastmilk if she were breastfeeding. She wouldn't usually need extra water though, unless she were constipated, and for a young infant, you should usually talk to your Pediatrician before giving your baby extra plain water.
The American Academy of Pediatrics actually states that "until your baby starts eating solid foods, he'll get all the water he needs from breastmilk or formula."
Another situation where you would give an older child extra water would be when they were getting overheated, but that shouldn't be happening to a newborn or infant. If your granddaughter got sick, she might also need extra fluids, but water wouldn't usually be the best choice in that situation. An oral rehydration solution, like Pedialyte, would be better, and again, under the supervision of your Pediatrician.
Changing Advice and OpinionsIdeas and opinions over things like this change over the years. I am sure that there are other things that you did for your daughter, who likely turned out just fine, as many grandparents like to remind me, that we don't recommend now. Some of these things are extremely important, like the new recommendations to keep newborns and infants sleeping on their backs to reduce the risk of SIDS, and others are less important, like this one about water or some of the stricter guidelines about the order of introducing solid baby foods.
When you disagree about something like this, it might help to go along to your granddaughter's well child visits to her Pediatrician so that you can discuss things and try to get your point across and to understand her doctor's view.
Are You Being Too Helpful?But also consider how you would feel when you were a new mom raising your daughter for the first time and someone was there telling you what to do or telling you that your Pediatrician was wrong. It is great that you are available to offer your help and expertise, but sometimes it is best to just offer your advice and opinions and why you did it the way you did and let a new mom decide what is best for her baby. She needs to have confidence in her Pediatrician too and the 'advice of the day' is that you not give water to younger infants unless there is a specific reason to do so.
I'm not saying that you are pushing your opinion, and it actually sounds like you aren't or you wouldn't be here asking for another opinion. But it can sometimes be hard for grandparents to balance simply being helpful with being 'too helpful.' If you aren't sure which type of grandmother or mother you are, then maybe ask. If you don't want to ask your daughter, then ask someone else. And keep in mind that this is general advice for anyone in this situation and may not apply to you and your daughter at all.
So When Do Babies Need Water?After they are six months old, infants do begin to need some fluoride, and so that is a good time to introduce some extra water into their diet, especially if they are breastfeeding, or simply prepare their iron fortified infant formula with fluoridated tap water.
But before six months, the average healthy baby doesn't need any extra water.