I actually looked this up on Breastfeeding.org... not sure if you're breast or formula feeding but hope it helps some...
Question:Should I give my baby water as well as breastmilk?
Answer: This is an often-asked universal question and there is a simple concise answer: NO! Use your breastmilk. Breastmilk is a perfect food for your baby. It has all the right components. The right amount of protein, fat, carbohydrates AND water. The composition of your milk changes as your baby's needs change and grow. The baby who is fed around the clock, on demand and is thriving will need no other supplementation.
In the beginning when you have colostrum, sometimes it seems as though there isn't enough. But most of the time, it is the exact amount your baby needs to start his or her life outside of the womb. It is the perfect food to flush out their little kidneys, move the meconium plug, eliminate excess bilirubin and satiate your baby until your full supply of mature milk starts to come in. If the baby is unable to remove the colostrum or milk from the breast due to a sucking or latch problem, help is indicated. The best help would come from a dedicated lactation consultant who can take the time to show you how to hand express or pump the colostrum or milk and get it into the baby via a different method (syringe, finger, cup, eye-dropper or tube) until the suck latch issue gets resolved. Use your breastmilk and a lactation consultant!
Water is not recommended in cases of newborn jaundice. Water can increase the bilirubin by decreasing the urge to breastfeed. Because only 2% of a baby's bilirubin is eliminated through the urine, while 98% (LLLI Breastfeeding Answer book, 1997) is eliminated through his bowel movement, the baby needs food to make the bowels move and eliminate the bilirubin. Once again, breastmilk is the perfect food!
All around the world, no matter where you live, sea level, high in the mountains, the arid deserts or the humid rainforests, breastmilk is best! A baby who is fed on demand around the clock, is thriving and has her or his nutritional needs met, is a well-hydrated, happy baby.
and this was helpful when talking about both breastfed and formula fedbabies: http://www.kellymom.com/nutrition/solids/baby-water.html
http://www.todaysparent.com/baby/foodnutrition/article.jsp?content=1240
Babycenter.com:
Should I give my newborn water or sugar water?
Expert Answers
David Geller, pediatrician
It isn't necessary to give your newborn water. Most babies get enough fluids from breast milk or infant
formula.
Even when a mother's milk supply is just coming in during the first few days after delivery, the baby is getting
colostrum,which is enough to keep the baby well hydrated. Because a newborn's kidneys are immature, she has a difficult time concentrating her urine, and if given too much plain water, may have trouble excreting it. This could lead to dangerous changes in the concentrations of sodium and potassium in her bloodstream. For these reasons, infants should not be given extra fluids unless their pediatrician recommends it.
When can my baby drink water?
Expert Answers
The BabyCenter Editorial Team
Hold off on giving your baby water until he's about 6 months old, and limit it to about an ounce or two at a time — ideally after meals. You don't want your baby to feel so full that he refuses to nurse or take his bottle. If your baby seems interested in taking occasional sips of water before 6 months of age, it's probably not going to hurt him. In fact, a little bit of water can help keep your baby hydrated in hot weather. But talk to his doctor if you're offering it before 6 months. Giving a baby younger than 6 months old too much water can interfere with his body's ability to absorb the nutrients in breast milk or
formula. In rare cases, babies who drink too much water can develop a condition known as "water intoxication," which can cause seizures and even coma. "Babies don't really need water, or any liquid other than breast milk or formula, until after their first birthday," says Rachel Brandeis, a registered dietitian in Atlanta. After age 1, water and milk are Brandeis's baby beverages of choice. "You want to be sure juices don't displace milk in a baby's diet," she says. Once your baby celebrates his first birthday, you can let him drink as much water as he wants.