Babies Go Through The 4-Month Sleep Regression. Your Blurry Brain Is Not Wrong.

We investigate why perfect infants suddenly keep waking up and what tired parents (like us) can do.
Jade Brookbank via Getty Images

For the first three-and-a-half months of my younger kid’s life, he was a magical unicorn among babies: a good sleeper.

Three years ago, his older brother screamed my husband and me awake every 45 minutes over those same months, so this time around we anticipated the same. When that didn’t happen, we could not believe our good fortune.

In the very beginning, our new baby was up every two hours to eat, but he’d settle down easily — and as the weeks wore on, he started giving us five-, six-, even seven-hour stretches of uninterrupted sleep.

Then about two weeks ago, the wheels came off the bus.

At first he added one extra wake-up a night, then it was two ... then chaos. My husband and I went from being relatively rested, functioning human beings to frazzled loons. We wished each other luck when we got into bed at night, whispering about how many wake-ups we’d face. One? Six? And what just happened to our formerly good sleeper?

We were, the internet told us, in the grips of something called the “four-month sleep regression.”

Horror stories of the four-month regression abound online. “This sleep regression truly is hell,” one parent lamented, describing an experience pretty similar to mine. “Tell me there is a light at the end of the tunnel!” another pleaded. (I counted at least 30 Reddit threads dedicated to the topic.)

There isn’t much research exploring why some babies who could sleep for long periods suddenly can’t. As with many aspects of parenthood, the lack of attention from the medical community leaves moms and dads without much recourse beyond comparing notes on the internet.

“When you do a Google search, it absolutely comes up. Parents clearly describe that their baby was sleeping better, and then all of a sudden, sleep regressed,” said Dr. Shalini Paruthi, medical co-director of the St. Luke’s Sleep Medicine and Research Center in Chesterfield, Missouri. “But you know looking through PubMed, journal articles and book chapters and trying to find something that specifically says ‘four-month regression,’ there’s not much.”

And The Doctor Says ...

Although the obvious resource, pediatricians aren’t necessarily the best for troubleshooting sleep disturbances. They have so much else to cram in during a baby’s four-month checkup — a physical, questions about feeding and reaching milestones, vaccinations. When it comes to sleeping babies, they tend to be focused on the safety issues.

The medical community hasn’t even agreed upon clear parameters for what constitutes a sleep problem for babies, according to the American Academy of Sleep Medicine. What one parent or one pediatrician sees as an exorbitant number of wake-ups might, to another, simply seem like part of the deal with infants.

Indeed, one possible explanation for the lack of scientific investigation could be that for anyone not in the thick of it, a crappy stretch of sleep here and there doesn’t sound like a particularly big deal. Babies’ sleep behavior is notoriously messy as they sort out their circadian rhythms and outgrow the startle reflex that tends to yank them awake for at least the first two months. The advice repeated to new parents ad nauseam is to nap when the baby naps and basically hold on for dear life.

But when you’re running on four hours of interrupted sleep a night and so wiped that it feels like your eyeballs are on fire, things like the four-month regression takes on an outsize role in your life — particularly when it seemed like things were just starting to come together a bit. Not all sleep-deprived parents struggle, but studies clearly demonstrate a link between poor sleep and postpartum depression. And given that one-quarter of new moms are back at work within weeks of giving birth, those early shifts in the baby’s sleep can have a huge impact on parents’ ability to function day-to-day.

Well, They’re Growing

So what’s actually going on? Experts readily acknowledge that the lack of specific research doesn’t mean sleep regressions aren’t real.

Between three and five months, babies are going through incredible leaps, Paruthi said. They’re growing a lot, so some simply start waking up hungry more often. Others may begin waking up at night because they’re learning new skills — like rolling over and communicating for the first time through smiles, cooing and laughter — and they’re psyched to try them out. Some start teething. Some have outgrown the swaddles they’ve been accustomed to since birth. Some start eating foods for the first time, which can lead to interesting gastrointestinal situations in the wee hours of the morning.

There is also a fundamental change occurring in the very nature and pattern of their sleep.

“Non-REM sleep is our deep, restorative sleep. ... REM sleep is when we tend to do most of our active dreaming, or vivid dreaming,” explained Dr. Ann Halbower, a pediatric pulmonologist and director of Sleep Medicine Research at Children’s Hospital Colorado. Roughly around four months, babies start cycling through non-REM and REM cycles more like adults do, which can lead to more awakenings as their little brains and bodies try to make sense of what’s going on.

“They’re developing a different non-REM to REM cycle. They’re also developing a different day-to-night cycle, they’re developing motor skills and they’re developing cognitive skills — and all this has to occur at the same time,” Halbower said.

“It’s actually a sleep development,” she added. “It’s really a progression, not a regression.”

Live Through The Phase

But few parents feel much like celebrating when their kid suddenly becomes a terrible sleeper; they want relief. And here is where the internet’s obsession with “sleep associations” comes in — the idea that 4-month-old babies are suddenly much more aware of the props they relied on to fall asleep at the beginning of the night and are incapable of falling back asleep without them. A baby who falls asleep eating and being rocked will need to eat and be rocked again when she wakes up at 1 a.m., 3 a.m. and 5 a.m., the thinking goes.

The American Academy of Sleep Medicine certainly agrees that sleep associations can be real, although they don’t really recommend encouraging them.

“At the three- to four-month mark, we know that most babies are physically capable of self-soothing and falling asleep by themselves at the beginning of the night,” said Natalie Barnett, a New York-based sleep consultant who said that roughly 80 percent of the parents she works with have babies between 4 and 6 months old.

Around this time, she recommends that parents take pains to put their babies down in the crib when they’re drowsy, but not asleep, and give them some space to learn how to self-soothe — even if that requires some crying.

Of course, “cry it out” methods — the broad catch-all for any kind of sleep training that involves letting babies fuss as they figure out how to self-soothe themselves to sleep — are wildly divisive among parents. The American Academy of Sleep Medicine generally says they’re effective. Some parents choose, instead, to offer extra soothing and hope everything falls into place eventually.

It Will End, Eventually

Ultimately, Paruthi said, most babies tend to sort out their sleep pretty well by six months or so — that is, up to a point.

“If you go to the sleep textbooks, you’re going to find that they all say this magic quote of ‘Babies should start sleeping through the night by six months,’” Paruthi said. “Well, if you dig into the fine details, ‘sleeping through the night’ in those textbook definitions is really only five or six hours straight.”

After which point, the internet tells me, there is apparently another common sleep regression around eight months. And then possibly again at a year. And then 18 months.

In the meantime, I’ll be drinking a hell of a lot of coffee.

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