Will a Snoo Smart Sleeper bassinet help with baby's sleep and crying?

What is the Snoo Smart Sleeper bassinet (sold by Dr Harvey Karp's business Happiest Baby)?

The Snoo Smart Sleeper bassinet costs about AU$2000, and can also be rented. Its motors are connected to a control app on your smart phone. The Snoo's design has a seductive, clean and contemporary aesthetic. It really is a compact and very attractive item for your bedroom! To use a Snoo, you

• Put your baby in a swaddle suit

• Place him on his back in the mechanised crib

• Secure him with clip-on wings so he can't roll onto his side or tummy.

When your baby wakes and fusses or cries, the Snoo automatically

• Switches on a pivot which swings or jiggles him from side to side

• Switches on an inbuilt white noise machine

• Increases the amount of movement and white noise as her crying increases

• Switches off altogether if your baby hasn't settled and you need to attend to her, according to various inbuilt algorithms.

Eight reasons not to purchase or rent a Snoo Smart Sleeper

You might be thinking about trying the Snoo because you're worried about your ability to manage broken nights. Or you might be feeling desperately sleep-deprived and willing to give anything a go. It's not wrong to experiment with a Snoo! But here are reasons why you might decide not to put money into a mechanised bassinet as you experiment your way through.

I have concerns that use of the Snoo might

1. Wake you in the night anyway, every time your baby begins to dial up. It's not safe to sleep your baby in another room day or night when she's under six months of age, regardless of Snoo use. But the mechanised bassinet's motors switch on and respond noisily as your baby starts to grizzle and cry.

2. Increase the possibility of damage to babies' sensitive and developing auditory systems. Audiologists recommend that 50 decibels averaged over an hour is the upper safe limit of white noise to avoid hearing loss. The Snoo plays white noise at between 65 and 70 decibels and as loud as 86 decibels if the baby is very dialled up. The American Academy of Pediatrics recommends placing white noise machines seven feet away from baby's head. Unfortunately, noise exposure has a cumulative effect on hearing. Even if baby's head is at the other end of the bassinet away from the in-built white noise machine, the sound can't be turned off unless the whole bassinet is turned off and used as a standard, non-mechanised crib. It could be many years before researchers are able to draw conclusions about this.

3. Take away your confidence that you can find ways to enjoy life and nights caring for your baby without using a Snoo!

   • In fact, underlying problems like unidentified breastfeeding or feeding issues or disrupted body clock settings are the main reasons baby sleep gets out of sync with parent sleep, which makes sleep feel out of control. The Snoo and the Five S's method don't address the real problems which result in serious sleep deprivation for parents.

   • Although the Snoo claims to make life easier, it actually adds unnecessary complications, including the need to swaddle your baby after feeds. Swaddling makes sleep harder rather than easier for many families, which is why I don't promote wrapping, swaddling, or restricting baby's arm movements. In another example, weaning baby out of the Snoo comes with instructions.

4. Even worsen your mental or emotional well-being, if using the Snoo accidentally narrows your attention on to sleep, and successfully persuades you that you need the Snoo to cope. As you'll see below, there's no (convincing or reliable) research to show that the Snoo will improve your or your baby's sleep, but the evidence does show that worrying about sleep worsens sleep. More importantly, the things that really do cause baby sleep problems are not dealt with by the Snoo.

5. Potentially delay some babies' motor development. This is because the Snoo straps babies to the mattress with a restrictive positioning device which doesn't allow baby to practice moving against gravity in the night, or when she wakes up after a sleep. As babies grow, they normally repeatedly reposition themselves on their sides or tummy to practice rolling. Some babies start rolling from 12 weeks or even earlier, which is why wrap or swaddle guidelines advise not wrap or swaddle after three months. There is great variability in baby motor development, so even if the Snoo results in a delay in motor development for some, this is likely to be temporary only.

... However, if Snoo use really does require you to attend less often to your baby in the night, and really does increase the amount of time your baby sleeps, as claimed despite lack of evidence, then there would be sound physiological and neurological reasons to be concerned that Snoo use might

6. Undermine breastfeeding success, including by delaying breastfeeds, because

   • Baby's level of hunger and distress needs to be higher in the Snoo than in an unmechanised setting, to secure a breastfeeding mother's attention for a feed.

   • Having to unswaddle baby becomes a barrier which may make you less likely to offer quick and frequent little breastfeeds (which are the best way to make sure you maintain baby's weight gain and your milk supply).

   A study showed that babies of parents who used Dr Harvey Karp's Five S's program, from which the Snoo model of baby care was developed, weighed less at 12 months of age.

7. Make it more likely that baby develops a flat spot on the back of her head. You can find out about positional plagiocephaly and your baby's motor development here, here and here.

8. Potentially increase the chances of a vulnerable baby having developmental challenges long-term. In my view, this concern may have some relevance for those little ones who

   • Are born prematurely

   • Have a neurodiverse sibling or a sibling with developmental challenges

   • Don't cue as much.

   Most babies are remarkably resilient to a wide range of infantcare practices, across diverse human cultures. The problem is that we don't know which little ones might be more vulnerable to long-term side-effects from a novel technological product like this mechanised bassinet. It could be many years before researchers are able to draw conclusions about this.

To help make sense of the growing popularity of the Snoo, and why families are turning to it, we need to think about

• Dr Karp's Five S's, because Dr Karp developed the Snoo as a mechanical way of delivering three elements of his Five S's system. You can find out about the Five S's, from the perspective of NDC or the Possums programs, here.

• Whether the message that the Five S's and the Snoo are effective, evidence-based ways to decrease baby crying and increase baby sleep durations (which has driven sales) accurately represents the research. I show here, and below, why I don't believe this is the case.

The research doesn't show that the Snoo Smart Sleeper bassinet decreases baby crying and improves patterns of baby sleep over time

• A quote from a blog on the Happiest Baby website states: "Is there SNOO research? Yes! For example, a 2020 study demonstrated that SNOO’s constant womb-like rhythms boost a baby’s sleep by an average of one hour a night. And after two months of use, SNOO increases a baby’s longest continuous period of nighttime sleep from about five hours to almost seven hours. In other words, SNOO buoyed babies’ consolidated, continuous sleep by 40%!" This study was by Okun et al, but it is published as an abstract only. That means that the study is not available for others to analyse in depth, and has not been peer-reviewed.

• A study by Moller et al 2019 shows shows that babies were less fussy overall when they were held by the parent, compared to being placed in the Snoo. But this is not the same as claiming that the Five S's and the Snoo are effective in dialling babies down and improving sleep.

• In 2023, a review was published which examined all the studies that have evaluated the Five S's and the Snoo Smart Sleeper bassinet. Out of 66 published studies, the authors only selected a study for analysis if it

  • Provided clear outcomes and conclusions

  • Was relevant to infants under two years of age.

  This resulted in just two eligible studies, which were Moller et al 2019 and Okun et al 2020 (abstract only), discussed above. You can see that neither provide evidence to support the claim that a Snoo decreases crying and increases sleep in babies over time.

• A quote from a blog on the Happiest Baby website states: "More than 90% of nurses surveyed agree that SNOO reduces infant fussing." Two 2023 studies by Gellasch et al showed that neonatal intensive care nurses in the United States liked the Snoo. These clinicians self-selected to respond to the survey, reporting that Snoos helped babies settle and decreased their workload on the ward. However, these nurses worked in neonatal intensive care (NICU) settings in an advanced economy which separates prematurely-born babies from their parents' bodies. These settings have not yet adopted the genuinely evidence-based Kangaroo mother care principles released by the World Health Organisation in 2023 and recommended for roll-out in neonatal intensive care units world-wide for clinically stable low birth weight babies. Kangaroo mother care cuts costs, decreases fussy baby behaviours, and improves neonatal outcomes. Wouldn't it be better for hospitals to invest in the implementation of Kangaroo mother care to address heavy clinical work loads in NICU, rather than investing in Snoos?

• About two-thirds of studies listed on the Happiest Baby website under the heading Research are posters and abstracts. To me, this suggests that the appearance of having a lot of studies to support the product (rather than actually being research-based through peer reviewed publication in credible journals) is commercially important for this company.

You can also find out here why the Five S's approach, from which the Snoo has been developed, misrepresents the findings of evolutionary biology.

Selected references

Conde-Agudelo A, L D-RJ. Kangaroo mother care to reduce morbidity and mortality in low birthweight infants. Cochrane Database of Systematic Reviews. 2016;2017(8):CD002771.

Douglas PS. Pre-emptive intervention for Autism Spectrum Disorder: theoretical foundations and clinical translation. Frontiers in Integrative Neuroscience. 2019; 13(66): doi.org/10.3389/fnint. 2019. 00066.

Gellasch P, Walsh TA, Geiger S. A descriptive evaluation of time savings and work experience among neonatal clinicians when using a responsive bassinet. Journal of Neonatal Nursing. 2023;29:781-785.

Gellasch P, Johnson S, Walsh TA. The experiences and perceptions of neonatal clinicians when using a responsive bassinet. Advances in Neonatal Care. 2023;23(4):e88-e95.

Happiest Baby: the blog https://www.happiestbaby.com/blogs/snoo/snoo-criticism#is-snoo-bad-for-development? Screenshot 5 March 2024

Happiest Baby: research https://health.happiestbaby.com/pages/research Screenshot 5 March 2024

Harrington JW, Logan S, Harwell C. Effective analgesia using physical interventions for infant immunizations. Pediatrics. 2012;129:815-822.

Karp HK. Evaluation of a womb-like sensory intervention to improve infant sleep. Sleep Medicine. 2023;100:S195.

McRury JM, Zolotor AJ. A randomized, controlled trial of a behavioral intervention to reduce crying among infants. The Journal of the American Board of Family Medicine. 2010;23 315-322.

Moller EL, De Vente W, Rodenburg R. Infant crying and the calming response: parental versus mechanical soothing using swaddling, sound, and movement. Plos One. 2019;14(4):e0214548.

Quin N, Tikotzky L, Astbury L. Preventing postpartum insomnia: findings from a three-arm randomised controlled trial of Cognitive Behavioural Therapy for Insomnia, a responsive bassinet, and sleep hygiene. Sleep. 2024:https://doi.org/10.1093/sleep/zsae1106.

Savage JS, Birth LL, M M. Effect of the INSIGHT Responsive Parenting Intervention on rapid infant weight gain and overweight status age age 1 year: a randomized clinical trial. JAMA Pediatrics. 2016;170:742-749.

Singh JK, Menahem S. The five "S's" and the "SNOO" Smart Sleeper - non-pharmacological interventions (NPI) to promote sleep and reduce crying of infants: a scoping review. Translational Pediatrics. 2023;12(8).

Sivanandan S, Sankar MJ. Kangaroo mother care for preterm or low birth weight infants: a systematic review and meta-analysis. BMJ Global Health. 2023;8:e0101728.

Last updated 5 March 2024