Sleep in SNOO Smart Sleeper Bassinet in Preterm Infants

Sleep plays an important role in the brain growth and development of preterm infants. Neonatal sleep is made up of three stages of sleep: quiet sleep, active sleep, and transitional sleep. Poor sleep can be a result of premature birth itself as well as from simply being in the neonatal intensive care unit (NICU) environment. The interruptions that these infants are exposed to include frequent cares, physical exams, lights, and noises.

The investigators are interested in the potential positive effects on sleep of recreating the environment of the womb. The SNOO is a bassinet that uses the combination of a secure swaddle, white noise, and gentle rocking movements to mimic the conditions that infants were exposed to in the uterus before being born. The investigators are interested in studying how recreating this environment of "within the womb" impacts the sleep-wake cycles of premature infants. To do this, the investigators will measure the amount of time that premature infants spent asleep versus awake while in the SNOO through behavior observations, electroencephalogram (brain activity monitoring), and vital signs. The investigators hypothesize that sleeping in the SNOO will increase the amount of time that the premature infants spend in quiet sleep and will improve their vital signs.

• SNOO Smart Sleeper (Device): Infants will be secured in the SNOO Sleep Sack. They will be placed in the center of the SNOO Smart Sleeper. The SNOO will be powered on and will start playing white noise and rocking from side-to-side. The SNOO's movement and sound settings will automatically ramp up and down as needed in response to the infant's sensed level of fussiness or crying per the manufacturer's programming. The "preemie mode" will be enabled, which caps motion at level 2 out of 5.
• Traditional bassinet (Device): Infants will be swaddled using a standard hospital blanket. They will be placed in the center of the SNOO Smart Sleeper, but the SNOO will be left powered-off. No white noise will be played. No side-to-side rocking motions will occur.

Primary outcomes

• Percent of Quiet Sleep Time During 3-hour Sleep Assessment [At baseline sleep assessment, up to 3 hours]: Quiet sleep is a marker of sleep maturation and will be measured by the researcher during the 3-hour-long sleep assessments. Quiet sleep defined as eyes closed with predominantly flaccid "rag doll" appearance, body movements limited to startles, and rhythmic jaw jerks lasting 1 to 2 seconds.

Secondary outcomes

• Change in Heart Rate Variability [At baseline sleep assessment (up to 3 hours) and second sleep assessment (up to 3 hours)]: Heart rate variability is the fluctuation of beat-to-beat heart rate intervals over time and is a marker of autonomic nervous system maturation.
• Change in Cerebral Oxygenation [At baseline sleep assessment (up to 3 hours) and second sleep assessment (up to 3 hours)]: Cerebral oxygenation is a measure of the oxygen content of brain and will be measured by near-infrared spectroscopy (NIRS).
• Change in Oxygen Saturation [At baseline sleep assessment (up to 3 hours) and second sleep assessment (up to 3 hours)]: Oxygen saturation is a measure of the oxygen content of the blood, as measured by pulse oximetry.
• Change in Intermittent Hypoxemic Event Frequency [At baseline sleep assessment (up to 3 hours) and second sleep assessment (up to 3 hours)]: Intermittent hypoxemic events are episodes where oxygen saturation is low for prolonged periods, as measured by pulse oximetry.

Sex: All, ages: 1 Week to 12 Weeks, accepts healthy volunteers

Inclusion Criteria:

* Inpatients at the Morgan Stanley Children's Hospital NICU.
* Singleton gestation.
* Gestational age 28w0d to 36w6d at birth.
* Postmenstrual age greater than 35 weeks at the time of the intervention.
* Weight greater than 1.8 kg and less than 11.3 kg.
* Stable thermoregulation in an open crib.
* Stable respiratory status on room air (no nasal cannula or CPAP).
* Normal head ultrasound (if obtained).

Exclusion Criteria:

* Congenital brain or spinal anomalies.
* Intracranial hemorrhage.
* Severe encephalopathy.
* Known or suspected genetic syndromes that could result in cerebral dysfunction.
* Airway anomalies that could result in sleep-disordered breathing.
* Bleeding diatheses.
* Status post surgery or minor surgical procedures (i.e. inguinal hernia repair, circumcision).
* Fetal opioid exposure.
* Administration of sedating agents over the past 24 hours.
* Ability to independently roll to hands and knees.

Participant flow

Outcome results

• Percent of Quiet Sleep Time During 3-hour Sleep Assessment (Primary), Mean, percent: SNOO Group 26.8 +/- 9.5; Traditional Bassinet Group 19.8 +/- 5.1
• Change in Heart Rate Variability (Secondary)
• Change in Cerebral Oxygenation (Secondary)
• Change in Oxygen Saturation (Secondary)
• Change in Intermittent Hypoxemic Event Frequency (Secondary)

Adverse events

Time frame: During sleep time (approx 3 hours) at baseline sleep assessment

Limitations and caveats: All infants were discharged from the NICU after the 1st sleep assessment and were therefore not able to do a 2nd sleep assessment as outlined in the protocol, so the results presented in this record only reflects data collected from one 3-hour sleep assessment.

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• Study Protocol and Statistical Analysis Plan (PDF, 2026-07-27)

• Rakesh Sahni, MD, Principal investigator, Columbia University