The 5 S’s are a set of soothing techniques designed to calm a fussy newborn by recreating the sensory environment of the womb. Developed by pediatrician Harvey Karp, the five steps are Swaddle, Side/Stomach, Shush, Swing, and Suck. They work best during the first three months of life, sometimes called the “fourth trimester,” when babies are still adjusting to life outside the uterus. Used together and in order, these techniques activate what Karp calls the “calming reflex,” a neurological response that settles a crying infant.
Why the 5 S’s Work
For nine months, your baby lived in a tight, warm, loud, constantly moving space. Then they were born into a world that is comparatively still, quiet, and wide open. That contrast is jarring. Babies in their first few months can actually cry from under-stimulation, a kind of sensory deprivation that feels wrong after everything they were used to in the womb.
The uterus was roughly 80 to 90 decibels, louder than a vacuum cleaner, filled with the constant whooshing of blood flow. Your baby was snugly contained, gently rocked by every step you took, and could suck on their fingers whenever they wanted. Each of the 5 S’s targets one of these familiar sensations. Individually, they help. Together, they can switch off even intense crying by telling your baby’s nervous system that everything is fine.
Swaddle
Swaddling recreates the snug pressure your baby felt 24 hours a day in the womb. It doesn’t trigger the calming reflex on its own, but it sets the stage. By containing your baby’s arms, the swaddle prevents the startle reflex (those sudden arm flails) from interrupting the other techniques. Think of it as the foundation that lets everything else work.
A safe swaddle is snug around the chest but loose around the hips and legs. You should be able to slide your hand between the blanket and your baby’s chest. The hips need room to flex and spread naturally, and the knees should stay slightly bent. Wrapping the legs too tightly or forcing them straight increases the risk of hip problems. The American Academy of Orthopaedic Surgeons specifically recommends allowing ample room for hip and knee movement.
Stop swaddling as soon as your baby shows any signs of trying to roll over. A swaddled baby who ends up face down is at serious risk for suffocation and SIDS. For most babies, this transition happens around 2 to 4 months.
Side or Stomach Position
Holding your baby on their side or stomach while you comfort them can quiet crying quickly. This position is calming because it takes pressure off the startle reflex and can ease gas discomfort. You can hold your baby along your forearm with their belly against your arm, or lay them on their side in your lap while you pat their back.
This one comes with a critical safety distinction: side or stomach is only for calming a baby who is awake and in your arms. It is never a sleep position. Every time your baby goes down to sleep, whether for a nap or at night, they go on their back. The side position is not a safe compromise. Studies show it’s unstable, and babies can roll from their side onto their stomach. Babies who are used to sleeping on their backs but are then placed on their stomach or side face seven to eight times the SIDS risk compared to babies who always sleep in those positions. Back to sleep, every time.
Shush
A loud, steady “shhhh” sound near your baby’s ear mimics the constant rush of blood flow they heard in the womb. It needs to be louder than you’d expect, at least as loud as your baby’s crying, to cut through and get their attention. Once your baby starts to calm, you can gradually lower the volume.
White noise machines can do this job for you, especially at bedtime, but volume matters. The American Academy of Pediatrics recommends keeping sound machines below 50 decibels, about the level of a quiet conversation. Place the machine at least two feet from the crib. Running it too loud or too close risks hearing damage over time, which is the opposite of what you want from a sleep aid. Many parents find it helpful to use a louder shushing sound by mouth during active crying, then switch to a lower-volume machine once the baby settles.
Swing
Your baby spent months being gently jostled with every move you made. Rhythmic motion recreates that experience. The key word is “jiggle,” not “shake.” You’re aiming for small, quick, gentle movements, like the vibration of a car on a smooth road. Always support your baby’s head and neck.
Research from 2014 confirmed what parents have known intuitively: crying babies who are picked up and carried immediately stop voluntary movements and crying, and their heart rate drops. You can achieve this motion by holding your baby and swaying, using a baby swing, gently bouncing on an exercise ball, or going for a walk or car ride. The movement should feel rhythmic and continuous rather than sudden or large.
Suck
Sucking is deeply calming for newborns even when no milk is involved. This is called non-nutritive sucking, and it’s a well-documented reflex that helps babies self-regulate. A pacifier, a clean finger, or nursing can all satisfy this need.
Beyond comfort, there’s a safety benefit. The American Academy of Pediatrics recommends pacifier use at sleep time to help reduce the risk of SIDS. The protective mechanism isn’t fully understood, but one hypothesis involves saliva: pacifier use increases saliva production, and saliva contains antibacterial compounds that may help protect against infections linked to SIDS. If you’re breastfeeding, most guidelines suggest waiting until nursing is well established (usually 3 to 4 weeks) before introducing a pacifier.
Using All 5 Together
The 5 S’s are designed to be layered in order, not picked from like a menu. Start with the swaddle to contain the flailing. Then hold your baby on their side or stomach in your arms. Add a loud shush near their ear. Begin gentle swinging or jiggling. Finally, offer something to suck on. You may not always need all five, but for intense crying episodes, the combination is far more effective than any single technique.
Timing matters too. These techniques are most powerful during the first three months. After that, your baby’s nervous system matures, the calming reflex fades, and they develop new ways to self-soothe. Some elements, like white noise and pacifiers, can remain useful well past the newborn stage, but the full 5 S’s sequence is really a tool for those early, intense weeks when crying peaks and parents are most desperate for something that works.