According to Dr. Karp, parents can start introducing sleep cues on baby's first night. "Everyone tells you you can sleep train at 3 or 4 months of age — they can't learn how to sleep before that," he says. "But how come they can learn bad sleep clues? Why can't they learn the good sleep clues? It's so transparently wrong, yet everyone keeps doing the same thing over and over again!"

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Along with swaddling, Dr. Karp says white noise is the key to the sleep puzzle. "In the womb, [babies] have a sound that is louder than a vacuum cleaner 24/7. So to be in a silent room is bizarre beyond belief for them," he says.

He adds there are two types of white noise: low and high pitches. High-pitched noises — like beepers, alarms, and sirens — are great for getting a baby's attention. But lower-pitched noises — like the rumble of a car, train, or plane — are more soothing and can lull you to sleep. "The sound in the womb is very low and rumbly because babies are underwater and water filters out the high-pitch sounds," Dr. Karp says. "Most of the machines, the apps, have the wrong sound. They have a shhhh, which is irritating as hell to parents and not helpful to a lot of babies too. Low pitch — like the sound of rain on the roof — that you play all night and at all naps encourages a baby to sleep. So it helps babies sleep in that fourth trimester [the first three months]."

Dr. Karp goes on to explain that if they are used to the white noise from birth, it will train them to put themselves back to sleep when they wake in the middle of the night. "At four months, when you stop swaddling and babies get nosy, they start waking up at night, and if they're in a totally quiet room, they call for your assistance. That's why everyone's doing sleep training at four months. But you don't have to do sleep training if you get them used to these cues earlier on — the swaddling and the low-pitch white noise CD. Then you wean the swaddling, and when your 4-month-old wakes up in the middle of the night, they hear the rrrrrrrr sound and think, 'Everything's fine, I can go back to sleep.' If they wake up in a quiet room, they scream for their mom because that's who was with them when they fell asleep originally."

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Once your tot is using white noise to go (and stay) asleep, will they have it forever? That depends on you, according to Dr. Karp.

"That's your choice at least for the first year. Parents always ask, don't they become addicted and stuck to it? And the answer is No. 1, they're addicted to it when they're born, so to go from having it 24/7 to none is way too abrupt for a baby. No. 2, you can wean it. The beauty of white noise, and swaddling for that matter, is you can wean it in steps. If you want to wean the sound, you just gradually lower the sound over a week or two and it's gone. Sleeping with your baby or nursing your baby to sleep, it's all or none. It's much harder to wean them off of that. Sleep cues are not a bad thing."

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It may sound counterintuitive, but Dr. Karp says it's essential to wake your baby as she's drifting off to sleep.

"When you have a little baby, it's OK to rock them to sleep and nurse them to sleep — in fact, you can't really stop them from falling asleep while they're nursing. However, they will get dependent on that. You [need to] feed your baby, swaddle your baby, turn on the white noise, and rock your baby to sleep. Then you slide them into the crib or bassinet and you wake them up — you tickle their feet or something and you wake them a little bit. They're drowsy, they're kind of drunk from the milk a little bit. They're swaddled, they have the white noise, so they tend to fall back asleep in five to 10 seconds. Or, at most, you jiggle the crib a little bit to get them back to sleep. In those 10 seconds, they're learning how to put themselves back to sleep in the middle of the night, without your help. So you can train a baby the wrong habits in the first few weeks, but you can also start training them the right habits in the first few weeks."

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Many parents become lax when sleep training their second, third, and fourth tots because they're afraid of waking their older siblings. According to Dr. Karp, there's no need to worry. If you're using the swaddling and white noise methods from birth, the baby shouldn't be making much noise.

He adds, "if you have a 5-month-old that isn't sleeping, start using the white noise. Give it four to five nights and see if that works. Probably 70 percent of the time you can finesse your way out of a sleep problem just by adding white noise. But if you're determined you're going to let your baby cry it out, with your older child, put white noise in his room."

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Putting an old wives' tale to rest, Dr. Karp emphatically says that rice cereal does not help a baby sleep longer. "When you look at it, why should it help?" he says. "Why would giving eight ounces of milk that's got a lot of fat and protein not help a baby sleep, but giving them one to two teaspoons of rice starch help them sleep? I mean, it's not quick-drying cement. It really goes through them just as quickly."

Source: Flickr user Philippe Put

Negotiating sleep with a vocal toddler or preschooler can feel like you're talking to a Neanderthal sometimes. Dr. Karp's developed the Twinkle Interruptus program to help train them to get to sleep. He says:

"So there's a broken record you get from doctors that you just close the door and let them cry and in three to four nights they'll learn to sleep on their own. It's torture! This fun little technique called Twinkle Interruptus can let you sleep train a toddler in seven days or less with zero crying.

So for five to six days you practice Patience Stretching that teaches toddlers to be more patient. The general technique is that when your child wants something, you almost give it to them, and at the last minute, you pretend to be distracted, making them wait a few seconds. Any child will wait five seconds. Once they learn to wait five seconds, then you extend it to 10, 20, 30 seconds. You practice it five times a day with little kids. What you're doing is rewiring the part of the brain that is the patience center. That week you start using white noise every night an hour before bedtime. It becomes a subliminal cue in the background that it is becoming time for bed. You also give your child a teddy bear or blanket.

Then you start Twinkle Interruptus. So when a child calls for you at 3 in the morning, you go to them to make sure they're not sick or vomiting, you see that they're really OK. You have the white noise playing, the teddy bear right there, so you sit in their bed, you snuggle up with them, you start to do your bedtime routine with them — sing a bedtime lullaby, whatever — and after about 15, 20 seconds of that, you say, 'Oh, one second, I just have to see daddy one second,' and you quick go out of the room or you quick go to the other side of the room for five to 10 seconds, they'll let you do that because they already learned over the past week that mommy comes back. Then you come back, you snuggle up, and you start doing your routine again, and then after a minute or so, you start doing the same thing. And then you leave for 10 seconds. Then again for 20 seconds. And maybe the next night you start at 20 seconds and then a minute. And usually by two to three nights they fall asleep waiting for you to come back in. And that's the end of it. You're doing it in a nice way, not going head to head with a Neanderthal."

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