If you’ve ever found yourself bleary-eyed at 3 a.m., wondering why your newborn seems to think it’s party time, you’re not alone. One of the most common challenges new parents face is the unpredictable—and often exhausting—sleep patterns of their babies.

But here’s the reassuring truth: this seemingly chaotic sleep is not only normal, it’s essential. In fact, those short bursts of sleep and frequent wake-ups play a critical role in your baby’s healthy brain development, growth, and the gradual formation of their internal clock. Understanding how newborn sleep works can help you feel more at ease, better equipped to support your baby, and maybe even find a little peace in the process.

Why Infant Sleep Health Matter

Infants spend more than half of their day asleep, and for good reason. Sleep is deeply tied to the rapid development occurring during this period. The architecture and timing of sleep evolve quickly in the first year, reflecting the maturation of both the brain and the body’s internal timekeeping system: the circadian rhythm. A natural developmental change, or ontogeny, occurs in human sleep over time that is actually a great reflection of brain health and development. A healthy full-term infant does not have the typical sleep cycle that you may be familiar with and is reviewed here. The brain is too immature to generate these signals. However, by 4-6 months of age, infants develop a more typical sleep cycle or “ultradian rhythm” that reflects 3 states: wake, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. NREM sleep progresses through increasingly deeper periods of sleep (stages 1-3) until reaching the stage in which humans dream (known as REM sleep). Young children cycle through these stages every 50-60 minutes, and, by age 5-6 years, they typically cycle every 90-120 minutes. Most people have about 4-6 sleep cycles each night.

In addition to changes in cycle length, age also influences the amount of time spent in each stage, as does the time of the night. A person with regular healthy sleep and circadian timing spends more time in slow-wave or NREM stage 3 sleep in the beginning of the night, and that amount decreases across the night. REM sleep, on the other hand, does the opposite. It is one of the last stages of the sleep cycle and progressively lengthens in duration across the night.

Numerous studies show that poor sleep in infancy is associated with emotional, cognitive, and behavioral challenges later in life.¹ Supporting healthy sleep from the earliest days of life is not only important—it’s protective.

According to sleep science consensus, newborns (0–3 months) typically need 14–17 hours of sleep per day, while older infants (4–11 months) need 12–15 hours.²

What Is Healthy Infant Sleep?

Healthy infant sleep is defined using a modified version of the six core dimensions of sleep health:

Satisfaction – Is the baby relatively calm and settled after sleep?
Timing – Sleep happens at developmentally appropriate times
Duration – Infants get enough total daily sleep within age-appropriate ranges
Regularity – Sleep-wake patterns become more predictable over time
Efficiency – Increasing stretches of sleep with fewer awakenings over time
Alertness – Infants are feeding and engaged appropriately when awake

Although subjective satisfaction may be difficult to measure directly in infants, parental observations and infant behavior (e.g., reduced fussiness, improved feeding) are important cues.

Key Milestones in Infant Sleep

Healthy infant sleep is defined using a modified version of the six core dimensions of sleep health⁴:

0–6 weeks: Sleep is polyphasic (spread across day and night) and should add up to ~14–17 hours per day.
6–12 weeks: Early circadian patterns emerge; begin to consolidate nighttime sleep.
4–6 months: Melatonin production increases; many infants start sleeping longer stretches at night and develop a typical sleep cycle or “ultradian rhythm.”
6–12 months: The circadian rhythm continues to strengthen, aligning with a more consistent sleep schedule. Light exposure, consistent routines, and feeding patterns all play a role in entraining the circadian rhythm during this period.

Circadian Development in the First Year

At birth, infants lack a mature circadian rhythm. Their sleep-wake cycles are fragmented, driven primarily by hunger and the need for care. However, by around 6–12 weeks, circadian signals begin to emerge as the suprachiasmatic nucleus, known as the brain’s “master clock,” starts to respond to environmental cues like light and feeding times.⁵

Want to learn more about the suprachiasmatic nucleus and circadian rhythm?
Check out our Sleep and Circadian Basics page.

Common Sleep Challenges in Infants

Sleep patterns in infants vary widely, but some common challenges include:

Sleep Regressions

Around 4 months, many infants experience a regression due to changes in brain activity and sleep architecture. Although distressing, this is a normal sign of neurologic growth. Consistent routines and earlier bedtimes can help support transitions.

Fragmented Sleep

Nighttime wakings are developmentally normal in the first 6 months, especially if related to feeding needs. After 6 months, most infants are capable of longer sleep stretches, and night wakings may be behavioral rather than physiological.

Delayed Circadian Entrainment

Low daytime light exposure and irregular routines can delay the development of a stable circadian rhythm. Morning sunlight, predictable feeding and wake times, and dim lights in the evening help set the internal clock.

Long-Term Impact of Sleep in Infancy

Early sleep problems can have lasting effects. Studies have linked poor infant sleep with:

• Increased risk of behavioral and emotional problems later in childhood. Research has shown that children with consistent early bedtime routines are better able to regulate their emotions, which in turn has long-term benefits on emotional and behavioral outcomes.⁶
• Greater likelihood of parental stress and depression, which in turn can impact infant development. Alternatively, some research shows that high maternal depression scores are not associated with sleep deficiency in infants.⁷

The Bottom Line

WCSN supports families and clinicians by translating the latest research into practical guidance and education—ensuring that early sleep health becomes a strong foundation for lifelong well-being.

To see how WCSN is advancing infant sleep and circadian science through education, collaboration, and research partnerships, visit our Support Our Mission page.

References:

1. Mindell JA, Moore M. Does sleep matter? Impact on development and functioning in infants. Pediatrics. 2018;142(6):e20182589. 
2. National Heart, Lung, and Blood Institute. How Sleep Works – How Much Sleep Is Enough? National Institutes of Health. March 24, 2022. Accessed May 30, 2025. https://www.nhlbi.nih.gov/health/sleep/how-much-sleep
3. Morse AM. Sleep and neurodevelopment. Pract Neurol. 2019;March/April:32-36.
4. Buysse DJ. Sleep health: Can we define it? Does it matter? Sleep. 2014;37(1):9-17.
5. Kok EY, Kaur S, Mohd Shukri NH, et al. The role of light exposure in infant circadian rhythm establishment: a scoping review perspective. Eur J Pediatr. 2024;184(1):112. 
6. Pudasainee-Kapri S, Zhang Y, Razza RA. Early bedtime routines and behavioral outcomes among children from low-income families: Mediating role of emotion regulation. Infant Behav Dev. 2025;78:102027. 
7. Kotlar B, Kotlar A, Sadikova E, et al. Whose sleep matters? Untangling the relationships between maternal sleep, child sleep, and maternal depressive symptoms in the first two years of life. Eur Child Adolesc Psychiatry. Epub ahead of print. March 11, 2025