Newborn sleep issues are no joke. Learn more about managing infant sleep from an expert, Dr. Harvey Karp.

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If you’ve ever struggled to soothe and quiet your little one to sleep (and what parent hasn’t?) we bet we can guess what your late night internet searches look like: Why is my newborn not sleeping? What do you do when your baby won’t stop crying? When do babies sleep through the night?

That’s why we’re glad to introduce you to a particular pediatrician: Dr. Harvey Karp, founder and CEO of Happiest Baby. You’ve probably already heard his name or at least heard about some of his ideas. Healthline Parenthood had the chance to catch up with Dr. Karp to get answers to some of your pressing sleep questions.

See what he had to say below, and check out the video of this chat and more great content on our Healthline Parenthood Instagram.

When should I expect my baby to sleep through the night?

Baby’s sleep is kind of like a roller coaster. It gets better, but then they get a growth spurt or a cold and it could fall apart. Usually by 5 or 6 months, baby is sleeping through the night.

What’s the right age for adding blankets or comfort objects to crib?

That’s usually about 9 months to a year. (Editor’s note: The American Academy of Pediatrics suggests at least a year.) Any earlier, we worry about baby getting their faces in those objects and having difficulty breathing.

What causes SIDS while baby is asleep?

That is still a mystery! Some babies, for whatever reason, forget to breathe in the middle of the night.

Having said that, there are a number of things you can do to reduce your baby’s risk of sudden infant death syndrome (SIDS).

  • Keep them on their back.
  • Keep them out of your bed. In your bed, they can roll into a pillow or blanket which can cause a lot of problems.

In addition, it’s great to breastfeed, keep the baby in the room with you, use a pacifier at night, don’t smoke in the house, and get your vaccinations!

The last thing to keep your baby safe at night is the SNOO. The baby that is swaddled gets secured to the bed so they can’t flip to an unsafe position.

If you’re not using SNOO, you’ll want to stop swaddling baby at around 2–3 months (whenever baby can roll over) because swaddled babies that have rolled over have more problems with breathing.

What’s a SNOO?

The SNOO is a bassinet created by Dr. Karp that incorporates a safe sleeping space, swaddling, white noise, and motion to create an ideal sleep environment for newborns. It is available for purchase or rental through the Happiest Baby shop.

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What are the key concepts in the book ‘Happiest Baby on the Block’?

There are three main ideas that I talk about in the book and streaming video: The fourth trimester, calming reflex, and 5 S’s.

The fourth trimester is the crazy idea that baby is born 4 months before they’re ready for the world. But your job after baby is born is to be one big walking uterus holding them, walking them, shushing them, and feeding them all throughout the day.

The reason the fourth-trimester idea is so important is because when the baby is in the womb, they have sound that is louder than a vacuum cleaner and constant rocking motion. So it’s odd for them after birth to be in a flat, still bed.

The calming reflex is an automatic behavior that every baby is born with that is almost an on switch for crying and an on switch for sleep that you activate doing five steps.

Those five steps are the 5 S’s: swaddling, side or stomach (but not during sleep), shushing, swinging, and sucking. All of these mimic the womb and switch on the calming reflex.

What’s the science behind SNOO?

The science behind SNOO is babies need rhythm. We all know babies love to be rocked and shushed. That’s how they fall asleep the best.

Just like you get used to your favorite pillow or blanket, babies are used to rhythmic sensations 24/7 in the womb. That’s why it’s so strange for them to fall asleep in a still, quiet bed.

By shushing and rocking them all night long, SNOO is kind of like driving around in the car all night. Babies just naturally sleep an extra hour or two of sleep each night when they have that rhythm.

The best thing about SNOO? It’s really a 24-hour helper! It’s there to rock and shush the baby and give you a hand when you need to cook dinner, help the other kids, take a shower, or just get some sleep!

How long should a baby sleep in the SNOO?

The SNOO is used for about 6 months. That’s the period where babies learn to be great sleepers and when they are at risk of rolling to an unsafe position.

How do you transition from SNOO to the crib?

It’s actually really easy! There is a weaning feature that gives baby sound without motion. The motion comes back if baby gets upset, but usually within days, baby is ready for the crib.