"It's natural for infants who nurse to want to eat more frequently," says Lawrence Gartner, M.D., chair of the executive committee section on breastfeeding for the American Academy of Pediatrics. Your own milk is relatively low in fat and protein, so it's digested more easily than formula. That means it passes through your infant's stomach a little faster -- so she feels hungry sooner.
A breastfed baby may also ingest a little less at each feeding than a formula-fed baby. Every time you nurse, your milk changes from a thin liquid to a thicker, slightly higher-fat substance. Your infant may feel satisfied -- and stop suckling -- shortly after that more-filling milk starts to flow. (Not to worry: She's most likely getting plenty to eat.)
Frequent night nursings can be pretty rough on you, but they're actually a good thing, especially in the first six months. They provide your baby with the nutrients she needs to stay healthy, help keep your milk supply from dwindling, and prevent your breasts from becoming engorged. In fact, if you try to make a ravenous baby wait to eat, she'll probably just get fussier and may not be able to settle down for a good meal.
You can try to make sure she goes back to sleep quickly: Don't turn on the lights, don't play with her, and forgo a diaper change unless she's soaked or uncomfortable. By the time she's 8 or 9 months old, she'll start to give up most of those wee-hour feedings.