Why it works: "Babies have a critical hunger for motion, both because they're used to lots of motion inside their mother's uterus and because it's a powerful stimulus for their development," says Sandy Jones, parenting expert and coauthor of Great Expectations: Your Baby's First Year (Sterling Publishing Co.). In fact, "motion plays a very powerful role in child development." One classic study demonstrated that twins who received inner-ear stimulation from rocking and swinging developed motor skills faster than those who didn't. The inner-ear stimulation your baby gets when you hold her on your shoulder and dance around the living room is also likely to increase her alertness -- she'll stop fussing to look around. Keep up a steady motion long enough, and the pleasant repetition of it may nudge your baby into sleep.
Soothing strategies: Swings, vibrating bouncy seats, and strollers are all sanity savers, but your own baby dance can be even more effective, if you find a rhythm that's just right to soothe your little one. When you're pregnant, the baby is likely to sleep while you walk around (and wake up to kick once you're sitting down), explains Dr. Karp. After they're born, babies continue to be lulled by movement. "I watched a grandmother bring a fussy baby into complete relaxation by holding the baby firmly against her shoulder and walking two steps forward and one step backward," says Jones. "She was careful to keep doing it until it got boring, and finally the baby let out this huge sigh and fell deeply asleep." Try experimenting. Some babies like just a little rocking; others like to really move. Many parents even swear by holding baby as they gently bounce on an exercise ball.