There isn’t a widely recognized “13-month sleep regression” the way there is at 4 months, 8 months, or 18 months. But if your 13-month-old suddenly started fighting sleep, waking at night, or skipping naps, you’re not imagining it. Several developmental changes converge right around this age, and they can absolutely disrupt sleep for two to six weeks before things settle down again.
What’s Actually Happening at 13 Months
Sleep regressions aren’t random. They’re tied to specific physical or developmental shifts, and 13 months is a busy time on both fronts. Three things tend to collide at this age: new teeth breaking through, a peak in separation anxiety, and the beginning of a major nap transition. Any one of these can cause night waking or nap refusal. When two or three hit at once, sleep can fall apart quickly.
The good news is that none of these causes are permanent. Once your child adjusts, sleep typically returns to normal without any lasting changes to their patterns.
First Molars and Nighttime Pain
Upper first molars typically erupt between 13 and 19 months, with lower first molars following close behind at 14 to 18 months. That means 13 months is right at the leading edge of molar eruption for many toddlers. Molars are significantly larger than the front teeth your child has already cut, and the discomfort can be more intense.
Teething pain tends to be worse at night when there are fewer distractions. If your toddler was sleeping through the night and suddenly starts waking and crying, molars are one of the first things to consider. You may also notice increased drooling, fussiness during the day, or changes in appetite. The disruption from any single tooth usually lasts a few days to a week, but since multiple molars can arrive in sequence, the overall period of interrupted sleep can stretch longer.
Separation Anxiety Peaks Around This Age
Separation anxiety typically peaks between 10 and 18 months, which puts 13 months squarely in the window. At this age, your child understands that you exist when you leave the room but doesn’t yet have a solid sense of when (or whether) you’re coming back. That’s a stressful combination at bedtime.
Common signs include crying when you leave the room at night, waking more frequently and refusing to settle without a parent nearby, and protesting being put down in the crib. These behaviors can look identical to a sleep regression, and functionally, they are one. Your child isn’t being manipulative. Their brain is processing a new and genuinely unsettling concept. This phase can last several weeks, though the intensity usually tapers gradually rather than ending all at once.
The Two-to-One Nap Transition
Around 13 months, many toddlers start showing early signs of being ready to drop from two naps to one. This transition is one of the biggest schedule shifts in the first two years, and it can make sleep messy for a while. Signs that the transition is starting include fighting or skipping the morning nap, taking increasingly short morning naps (30 minutes or less), refusing the second nap three or more days out of five, or pushing the first nap past 10:30 a.m. so the second nap lands too late in the afternoon.
One important thing to know: this transition isn’t a light switch. It can take a couple of weeks to settle into a consistent one-nap schedule, and during that in-between period, some days will need two naps and others will work better with one. If your child starts waking unusually early (before 6 a.m.), that’s often a sign they’re overtired and temporarily need the second nap back.
At 13 months, recommended wake windows are 3 to 4 hours between sleep periods, with a goal of about 2.5 to 3 hours of total daytime sleep. If your child is still on two naps, keeping total daytime sleep at or under 3 hours helps protect nighttime sleep. If they’re transitioning to one nap, that single nap will need to be longer and fall closer to midday.
How Long This Phase Lasts
Most toddler sleep regressions last between 2 and 6 weeks. The wide range reflects how many factors can overlap. A child dealing only with teething might bounce back in a week. A child navigating molars, separation anxiety, and a nap transition simultaneously could take the full six weeks. The duration also depends partly on how consistently you respond during the disruption, since new habits formed during a regression (like bringing your child into your bed every night) can outlast the regression itself.
What Helps During This Phase
The single most effective strategy is keeping your bedtime routine consistent, even when your child is resisting it. A predictable sequence of events, like a bath, a book, and a cuddle, serves as a signal that it’s time to wind down. Doing the same thing every night gives your toddler something reliable to anchor to, which is especially helpful when separation anxiety is running high.
If your child seems newly anxious about the dark or about being alone, a soft nightlight can make a real difference. Choose one with a gentle, warm glow rather than anything bright enough to interfere with sleep. This small change gives some toddlers enough comfort to settle without needing a parent in the room.
Screen time before bed is worth watching at this age. The stimulation from phones and tablets can interfere with the ability to fall asleep, so keeping screens out of the last hour before bedtime helps your child’s brain shift into a calmer state.
For teething discomfort specifically, a cold washcloth to chew on before bed and appropriate pain relief (ask your pediatrician about dosing) can reduce the number of overnight wake-ups. Teething pain tends to come in waves, so even a few nights of relief can prevent a short disruption from becoming a longer pattern.
Perhaps the hardest advice: try not to introduce new sleep associations you don’t want to maintain long-term. It’s tempting to rock your toddler to sleep every night during a rough stretch, but if that wasn’t part of your routine before, it can become a new expectation that’s difficult to undo. Offer comfort and reassurance, but when possible, let your child practice falling back to sleep in their usual way.