There’s no sweeter sight than a sleeping baby — especially if you happen to be a bone-tired parent. But the poor baby who wails for hours, unable to find relief, may stir up darker feelings.

Tortured by lack of sleep and a screaming infant, some parents and caregivers lose control. Studies show that “colicky” babies and infants who can’t stop crying are at higher risk for shaken baby syndrome, which can cause permanent brain damage and even death.

Harvey Karp, MD, has a solution for parents, especially those at their wit’s end. A pediatrician and assistant professor of pediatrics at the University of California School of Medicine, he has attracted a devoted following among parents seeking a good night’s sleep for their children — and themselves.

The author of The Happiest Baby on the Block series, Karp has recently written a book called “The Happiest Baby Guide to Great Sleep: Simple Solutions for Kids from Birth to 5 Years.” The idea of sleep in babies, he says, “has been totally misunderstood.”

A “fourth trimester” of pregnancy?

For decades, pediatricians have talked and written about the “colicky” baby — one who cries uncontrollably for three hours a day or more and is extremely difficult to put to sleep. But Karp says true cases of colic are extremely rare, and doctors have found only 10 to 15 percent of “colicky” babies have a medical problem that explains their pain and crying. Karp’s theory is that the inconsolable baby is missing life in the comfortable womb.

In a sense, the first months of a baby's life outside the womb are the “fourth trimester” of pregnancy, Karp says, since humans give birth to babies whose brains are much less mature than those of many other mammals when they leave the womb.

“It’s little wonder babies have a hard time getting to sleep,” he says. “We need to recognize that they’re evicted from the womb three months before they're ready for the world.”

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Their protest about this eviction mean some parents may be sleep-deprived for weeks or months. Karp points to medical studies showing that people who get less than 6 hours of sleep a night have the reflexes and cloudy thinking of someone who is intoxicated. Parents (and other adults) who don’t get enough sleep are also more vulnerable to anxiety, depression, driving accidents, obesity and child abuse, according to recent studies.

“Lack of sleep,” Karp concludes, “is a major public health hazard.”

Self-soothing = peaceful baby

While there’s no sure-fire way to get a fussy baby to sleep, Karp and some other experts say parents can get more rest if they can teach their babies one basic skill: self soothing, so they can fall asleep again when they wake up.

“People often ask how old their babies should be before he sleeps through the night,” Karp says. “That’s just a huge myth. Nobody sleeps through the night.” As Karp explains, babies — like everyone else — awaken several times each night. And when babies can’t put themselves back to sleep, they and their parents suffer.

How to teach babies this crucial skill? Practice. As he explains, it’s completely natural — wonderful, even — for a baby to fall asleep in his mother’s or father’s arms. “It’s practically impossible to keep a tired baby from falling asleep while nursing,” he says. But instead of always laying a sleeping baby down in his crib, Karp recommends giving him a gentle jostle once in a while until his eyes open. Then you can set him down in the crib and, if all goes according to plan, he’ll fall asleep again on his own.

Karp knows many parents worry that waking a sleeping child is just asking for trouble. But he says the maneuver really works to teach a baby how to soothe himself.

The Five S’s sleep method: Replicating life in the womb

Karp has also developed a sleep plan based on ancient wisdom and the idea that parents should try to make the sleep environment as similar as possible to the womb. Here is what he calls his “Five S’s” approach to baby sleep.

Swaddling. Securing a baby snugly in a blanket or some other wrap is an ancient approach to bedtime. When done properly, Karp explains, swaddling calms babies partly because it mimics the tight quarters of the womb and prevents babies from thrashing around in the crib. Most of all, swaddling lets the baby know that it’s time to sleep.

You may need some instruction to get all of those tucks and folds exactly right, though. “Swaddling isn’t just wrapping a baby in a blanket,” Karp says. “The baby will try to struggle out of it. You have to know how to do it right.” (You can learn his swaddling technique by watching his videos on YouTube or his website.) Karp recommends swaddling babies before every sleep time, whether a mid-day nap or going down for the night.

Shush. White noise replicates the sounds of life in the womb, including the repeated “whoosh” of blood flowing through arteries. (“It’s as loud as a vacuum cleaner in the womb,” Karp says.) Parents also do this by saying “Shush” as the baby is going to sleep.

If a baby falls asleep before swaddling, perhaps while nursing, Karp advises waking her up, turning on the white noise or shushing, swaddling and setting her down. “She’ll be asleep again in 10 seconds, especially if she’s still a little drunk on milk,” he says.

Most babies can be weaned off swaddling after about four months, Karp says, adding that it’s easier if you continue to use white noise at bedtime.

Swinging. Some babies seem to need a rocking or swinging motion to fall asleep in your arms, another leftover from their days of floating around in the womb, Karp says. He suggests a short, tight swing, more like a jiggle, to replicate movement in the womb. In case you’re considering a baby swing, the American Academy of Pediatricians says never to let babies go to sleep in a swing because they could be injured or worse if their head gets caught in the cords.

Side position. Many babies get ready to sleep easier in a side position, Karp says. He recommends positioning a drowsy baby in your lap sideways, and when he’s dropping off to sleep, roll him on his back. Because of the risk of sudden infant death syndrome (SIDS), the best, safest sleep position for babies is always on their back.

Sucking. Sucking on your finger or nursing is extremely comforting for your baby, Karp says. Combining this and the other “S’s”, he says, make sleep almost irresistible if done right. Other soothing techniques that imitate the womb environment include wearing your baby in a sling, skin-to-skin contact, warm baths and gentle massage, he adds.

A cautionary note on swaddling

A Dutch report published in the journal Pediatrics noted that swaddled infants do seem to sleep longer than other babies — but the authors also raised some concerns about swaddling. For one, it’s possible for a swaddled baby to overheat. The report also said that a swaddled baby laid face down could be at risk for SIDs. The researchers concluded that swaddling is generally safe, but only when done correctly.

Related: The Sleep-Safe Baby Guide

Karp believes such worries shouldn’t stop parents from swaddling. “A baby can get overheated, especially in a hot room. Just always wrap them in a light blanket, never cover the head and check to make sure they aren’t too hot,” he says. Swaddled or not, babies should never be put to bed face down or on their side.

Karpand the AAP also say that it’s best if an infant can sleep in the same room as his parents. Karp recommends a bedside bassinet or crib. Studies show that sharing a bedroom with your baby reduces the risk of sudden infant death syndrome. And it’s undeniably more convenient when a baby wakes up with middle-of-the-night hunger pangs.

For those of you with sleepless babies, the good news is that eventually they grow out of it. And even the most worn-out of you get some rest. But if these “fourth-trimester” techniques work for you, you may get that sleep a lot faster.

Related: 8 Ways to Get the Sleep You Need for a Healthy Pregnancy

Chris Woolston, M.S. is a freelance writer and editor who specializes in science, health and travel. A reformed biologist, Woolston says, he studied algae and nitrogen dynamics in Antarctic lakes before the Science Writing Program propelled him out of the lab. He is a contributing editor at, a former staff writer for Time Inc.’s Hippocrates magazine, and co-author of Generation Extra Large (Perseus). He lives in Billings, Mt., with his wife – novelist Blythe Woolston – and their two children.