Newborns sleep 11 to 17 hours a day because their brains are growing at a pace they’ll never match again. All that sleep isn’t downtime. It’s when the most critical wiring of the nervous system takes place, fueled by an enormous metabolic demand that leaves little energy for anything else. If your baby seems to do nothing but sleep, eat, and sleep again, that’s exactly what’s supposed to happen.
Sleep Builds the Brain
A newborn’s brain roughly doubles in size during the first year of life, and sleep is when most of that construction happens. During “active sleep,” the newborn equivalent of REM sleep, babies twitch, smile, make sounds, and move their eyes beneath closed lids. This isn’t restlessness. Research at UMC Utrecht found that premature babies who spent a higher percentage of their sleep in this active phase had more white matter in their brains. White matter is the insulation around nerve fibers that allows different brain regions to communicate quickly and efficiently.
About half of a newborn’s total sleep is spent in REM, compared to roughly 20 to 25 percent in adults. That ratio exists for a reason: the infant brain is forming millions of new neural connections every day, and active sleep appears to be the state in which those connections get tested and strengthened. As the brain matures and the pace of new wiring slows, the proportion of REM sleep gradually drops.
How Newborn Sleep Cycles Work
A newborn’s sleep cycle moves through the same basic stages adults experience: lighter sleep, deeper sleep, then REM. But the entire cycle is much shorter, often only 45 to 50 minutes compared to the 90-minute cycles adults have. Babies cycle through these stages multiple times during a single stretch of sleep, which is why they seem to shift between still, quiet sleep and twitchy, noisy sleep so frequently.
These short cycles also explain why newborns wake so often. Each time they transition between cycles, there’s a brief window where they’re more likely to stir. Combine that with a stomach roughly the size of a walnut that empties quickly, and you get the classic pattern: sleep for a couple of hours, wake to eat, fall back asleep almost immediately.
Growth Spurts Make Them Even Sleepier
If your newborn suddenly seems to sleep even more than usual, a growth spurt is a likely explanation. These typically hit at predictable points: around 2 to 3 weeks, 6 weeks, 3 months, 6 months, and 9 months. During a growth spurt, the body releases more growth hormone (which peaks during deep sleep), and babies often respond by sleeping longer stretches or napping more frequently. You’ll also notice changes in appetite, sometimes hungrier, sometimes less interested in feeding, along with more general fussiness. Growth spurts usually resolve within a few days.
Normal Sleepiness vs. Something More
The tricky part is that “very sleepy” is baseline normal for a newborn, so it can be hard to tell when sleepiness crosses into lethargy. The difference comes down to what happens when the baby is awake. A healthy sleepy newborn, once roused, will be alert, make eye contact, respond to your voice, feed well, and can be comforted when crying. A lethargic baby is different: they’re difficult to wake for feedings, and when they are awake, they seem drowsy and sluggish, not tracking faces or reacting to sounds. Their body may feel limp.
One common medical cause of excessive sleepiness in the first week is jaundice, a buildup of bilirubin that gives the skin and eyes a yellowish tint. Mild jaundice is extremely common and usually harmless, but when bilirubin levels climb too high, babies become notably harder to wake. If your newborn’s skin looks increasingly yellow, they’re difficult to rouse for feeds, or their cry sounds weak, those are signs to get checked promptly.
Hydration is another useful signal. Six to eight wet diapers a day is normal for a newborn getting enough milk. Fewer than three or four wet diapers in 24 hours suggests dehydration, which can both cause and result from too much sleeping and not enough feeding.
How to Wake a Sleepy Newborn for Feeding
In the first few weeks, most pediatricians recommend feeding at least every two to three hours, even if it means waking the baby. Some newborns make this easy. Others sleep like they’ve been sedated. A few reliable techniques can help.
- Start gentle. Pick your baby up, talk or sing to them, move their arms and legs, tickle the bottoms of their feet, or stroke their cheek.
- Undress them. Many newborns hate being undressed. Whether it’s the physical sensation or the cool air on their skin, stripping down to a diaper is often enough to get their eyes open.
- Change the diaper. Even if the diaper is clean, going through the motions of a change adds enough stimulation to help. The combination of undressing, repositioning, and cool air works well together.
- Try a bath. If nothing else works, a lukewarm bath takes stimulation a step further. This is the last resort, but it’s effective.
The goal isn’t to fully wake the baby into a playful state. You just need them alert enough to latch and feed. Once they’ve eaten, they’ll almost certainly drift right back to sleep, and that’s fine.
When the Sleepiness Starts to Lift
Around 6 to 8 weeks, most babies begin spending slightly more time awake during the day. Their sleep cycles start to consolidate, meaning longer stretches at night with more distinct wake periods during daylight hours. By 3 to 4 months, many babies have shifted toward a pattern that more closely resembles day-night organization, though they still need 12 to 16 hours of total sleep. The intense sleepiness of the newborn period is temporary, driven by a brain that’s building itself at breakneck speed and a body that’s growing faster than it ever will again.