Some babies, however, may need an extra boost, notes Marianne Neifert, M.D., Denver pediatrician and author of Dr. Mom's Guide to Breastfeeding. If it looks like your baby may be losing too much weight or is jaundiced or premature, talk to your baby's doctor right away. He may suggest supplementing with formula for a few days, Dr. Neifert says. "The more well-nourished your baby is, the more effective he'll become at breastfeeding."
If you need to supplement, don't worry about "nipple confusion" -- the idea that a baby who's given a bottle too early will prefer it to the breast. Nipple confusion is more likely with a baby who is having trouble with the mechanics of breastfeeding, like latching on, rather than a result of a milk supply problem, says Dr. Neifert. It isn't that the baby is confused, but that she discovers where it's easier to get food and gives up on the breast. If your milk isn't in by the third day, tiding your baby over with a bottle may keep her calm and give you some rest. Just keep nursing, says Dr. Neifert, so she stimulates your milk production and practices latching on.