Developmental Leaps and Sleep Regressions: What’s the Deal?

If you’ve ever Googled “why is my baby suddenly not sleeping?” at 2 a.m., you’re not alone. You’ve probably heard of the infamous 4-month sleep regression. But what about the others? Sleep regressions commonly occur at 9 months, 12 months, 18 months, and again around 3 years old (or whenever a child transitions from a crib to an open bed).

What is a Sleep Regression?

A sleep regression is a period when a baby or toddler, who was previously sleeping well, suddenly starts waking up frequently, resisting naps, or struggling with bedtime—often out of nowhere. Unlike teething, there’s no obvious physical cause, like pain or illness. (And honestly? Most sleep disruptions blamed on teething aren’t actually caused by erupting teeth.)

Instead, sleep regressions typically happen when a child is experiencing a major developmental leap. At 4 months, babies’ sleep shifts from a newborn pattern (where they can doze off in a noisy room) to a more structured sleep cycle that includes REM sleep. Their increased social awareness means they now have a serious case of FOMO—so you may need to take them to a quiet space to eat and sleep.

Sleep Regressions by Age
 
4-Month Sleep Regression

What’s happening: Babies transition from newborn sleep cycles to more adult-like sleep patterns, waking up more frequently between cycles.

How to handle it: This is a great time to establish strong sleep habits and routines. Teaching independent sleep skills can help them settle between cycles.

9-Month Sleep Regression

What’s happening: Around this time, babies develop separation anxiety, start crawling, and pull up to stand. Many wake up to practice their new skills or check that you’re still nearby.

How to handle it: Give plenty of practice time during the day for new motor skills, provide extra reassurance, and reinforce a consistent bedtime routine.

12-Month Sleep Regression

What’s happening: Taking those first steps and the transition to fewer naps can cause night wakings or nap strikes. Some toddlers also begin testing boundaries.

How to handle it: Stick to a predictable schedule and avoid dropping naps too soon. Encourage soothing techniques that don’t involve rocking or feeding to sleep.

18-Month Sleep Regression

What’s happening: Toddlers develop their own agendas, test boundaries, and experience a surge in independence. Many are also running and jumping.

How to handle it: Stay consistent with bedtime rules, offer extra reassurance, and avoid making big sleep changes during this phase.

Crib-to-Bed Transition Sleep Regression

What’s happening: Moving from the security of a crib to the freedom of a bed can be overwhelming. Toddlers often get out of bed repeatedly, test limits, or struggle with falling asleep without the familiar crib enclosure.

How to handle it: If you haven’t transitioned yet, toddler-proof the room first. Use a doorknob cover to keep them from leaving at will, and never introduce the habit of lying down with them to fall asleep—unless you want a long-term bed partner!

How to Get Through a Sleep Regression

If you haven’t sleep trained yet, now is the perfect time.

Counterintuitively, sleep training actually builds confidence. When a child knows they can fall asleep and stay asleep on their own, they feel secure in the knowledge that you’ll come back when sleep time is done. For babies who rely on an adult to sleep, sleep becomes an anxiety-ridden experience because they have no control over their rest.

If you’ve already sleep trained, the good news is that sleep regressions tend to be shorter and less severe. If your child suddenly starts waking up at night, first check for physical discomfort—illness, temperature issues, or a dirty diaper. If everything checks out, reinforce your existing sleep training method (whether CIO, timed checks, or the chair method).

The key is consistency. Most kids return to great sleep in just 2-3 nights.

PS If your family is stuck in a sleep regression, you’re not alone. I can help. Set up a free consult, and let’s get you unstuck in two weeks or less--guaranteed.