Happiest Baby on the Block Review: Do the 5 S's Work?

The Happiest Baby on the Block is Dr. Harvey Karp’s newborn calming method, built around the 5 S’s: swaddle, side or stomach position, shush, swing and suck. They are calming techniques for a crying baby, not a sleep-training plan, and in that role they’re worth learning. The evidence is thinner than the reputation. One small randomised trial found the method, taught by video, did not reduce crying. And two of the S’s have hard safe-sleep limits: the side or stomach hold is for soothing in your arms only, and swaddling stops when your baby starts trying to roll.

I make my living in this industry, and almost every newborn course I’ve reviewed borrows from this book. Here’s what it is, what holds up, and where you need to be careful.

What are the 5 S’s?

Karp’s own guide to the 5 S’s lists them as Swaddle, Side-Stomach Position, Shush, Swing and Suck. His theory has two parts. He calls the first months a “fourth trimester,” because human babies are born early by his reckoning. And he says babies have an inborn “calming reflex” that sensations like those in the womb can switch on. In his own words:

• Swaddle. A snug wrap with “arms snug and straight at their sides” and hips “loose and flexed,” used only during fussing and sleep, and stopped “once your baby can roll over.”
• Side or stomach position. Holding the baby on their side, their stomach or over your shoulder. He is clear: “it is NOT safe to place a baby on the side or stomach to sleep. The back is the only safe position for sleeping.”
• Shush. Loud, rumbly white noise, since the womb is noisy.
• Swing. Small, fast jiggling motions while you support the head, which he calls the “Jell-O head jiggle.” He warns that all-night swinging in a baby swing “is very dangerous.”
• Suck. A pacifier or feed, with the advice to wait until breastfeeding is well established before offering a pacifier.

The book is the method’s full version, and the revised second edition is the current one in print.

The safe-sleep lines, stated first

Two of the S’s sit close to real infant-sleep risks, so here are the limits before anything else.

The side and stomach hold is for your arms, never for sleep. The AAP’s safe sleep guide says that “the side position is just as dangerous as the stomach position.” Once your baby is calm or drowsy, put them down on their back, on a firm, flat surface, every time. Karp says the same, and I’m repeating it because this is the S that gets misremembered.

Swaddling stops at the first signs of rolling. The same AAP page says: “When your baby looks like they’re trying to roll over, you should stop swaddling them,” and notes that rolling “usually happens around 3 to 4 months, but it can happen earlier.” It also says swaddling “doesn’t reduce the risk of SIDS,” that a swaddled baby must always be on their back, and that weighted swaddles shouldn’t be used.

The swing is a movement, not a place to sleep. If your baby falls asleep in a swing, a car seat or a carrier, the AAP says to move them to a firm sleep surface on their back as soon as possible.

Happiest Baby also sells the SNOO, a powered bassinet, and says babies in it can stay swaddled longer because it keeps them on their back. That’s a device claim, and device reviews aren’t my lane. Only Mom Reviews has covered whether the SNOO is worth it properly.

Do the 5 S’s work?

Two honest answers, and they don’t contradict each other.

As a calming toolkit, they hold up in practice. In consults, the pattern I see is that parents who learn a firm swaddle, loud enough white noise and small fast jiggles handle the evening fussy period better than parents who just rock and hope. Every piece is old: parents have swaddled, shushed and rocked for centuries. Karp’s contribution is the packaging, the order and the confidence to do it more firmly than feels natural.

As a way to reduce overall crying, the trial evidence is weak. A randomised controlled trial in the Journal of the American Board of Family Medicine in 2010 gave new mothers a video of the five techniques and compared them with mothers shown a standard newborn-care video. Fifty-one mother-baby pairs started and 35 finished. There were no statistically significant differences in daily crying or sleep at any point measured over 12 weeks. The authors concluded the method, “when provided via videotape, does not seem to be efficacious in decreasing total crying among normal infants.”

That’s one small trial, with heavy dropout and a video instead of hands-on teaching. It doesn’t prove the techniques are useless. It does mean that a strong claim that the 5 S’s will dramatically cut your baby’s crying goes beyond the evidence. Use them to calm a crying baby in the moment, and don’t expect them to change your baby’s overall temperament.

Where it’s genuinely useful

The newborn weeks, when nothing else applies. Under about four months there’s no sleep-training method to run, and the no-cry approaches come later. A calming toolkit is what newborn parents actually need, and this is the best-organised one available.

Parents who are scared of the crying. Karp’s page links prolonged crying with parental exhaustion and postpartum depression risk. Having a plan for the evening fussy period does as much for the parent as for the baby.

Partners and grandparents. The S’s are easy to teach. Anyone can learn a jiggle and a shush, which spreads the load in a way feeding to sleep can’t.

Where it falls down

“Calming reflex” is presented more confidently than the evidence allows. It’s a useful idea and a good teaching device. It isn’t settled science.

It’s tied to products. The free guide links to the company’s swaddle, sound machines and bassinet throughout. You don’t need any of them for the method. A large thin blanket, a basic white-noise source and your arms will do.

It stops at the newborn stage. The method is about calming, not long-term sleep. When your baby is past about four months and nights are the problem, you need a different approach. My comparison of sleep training methods is the next step.

The free version of this advice

House rule: every review names the no-cost route first. Karp’s own 5 S’s page sets out the whole method for free, and your library will almost certainly have the book. White noise needs no special device. I’ve set out the volume and placement rules in my white noise setup guide, and any steady source works. The only thing worth paying for is practice: swaddle a doll a few times before you’re trying it at 2 a.m.

What I’d tell a client

Learn the 5 S’s before the baby arrives and practise the swaddle and the jiggle until they’re automatic. Use them to calm a crying baby, then put your baby down on their back in a bare crib. The side or stomach hold happens in your arms only. Stop swaddling the moment your baby starts trying to roll. Don’t expect the method to change how much your baby cries overall, because the one trial we have didn’t find that. And if the crying is relentless, comes with fever, poor feeding or vomiting, or just feels wrong to you, don’t try more S’s. That’s a pediatrician conversation, full stop.

FAQ: Happiest Baby on the Block

What are the 5 S’s?

Swaddle, side or stomach position, shush, swing and suck, as Harvey Karp sets them out. Together they’re meant to calm a crying newborn by imitating sensations from the womb.

Is the side or stomach position safe?

Only as a hold while your baby is awake and in your arms. For sleep, always lay your baby on their back. The AAP says side sleeping is as dangerous as stomach sleeping.

When should I stop swaddling?

When your baby looks like they’re trying to roll over, which the AAP says usually happens around 3 to 4 months but can happen earlier. Always place a swaddled baby on their back.

Do the 5 S’s reduce colic?

They can calm a crying baby in the moment. One 2010 randomised trial of the method taught by video found no difference in total crying over 12 weeks. If crying is constant or worrying, talk to your pediatrician.

Is Happiest Baby on the Block a sleep training method?

No. It’s a calming method for the newborn months. Sleep training comes later, usually after about four months, and is a separate decision.