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The “Four-Month Sleep Regression”: What Is It, and What Can Be Done About It?

(Revised and updated from an earlier version.)

At Baby Sleep Science we don’t like the term “four-month regression,” because the changes in sleep that occur around 3–4 months old aren’t really a regression at all; they result from a permanent change in sleep architecture.

The Science

When a baby is born, sleep is immature and nearly constant. A healthy newborn (free of colic, reflux or other medical concerns) will sleep until one of three things happens: 1) hunger, 2) another need (wet/dirty diaper), 3) sleep is no longer needed. This pattern is difficult at first, but for most families sleep unfolds as you expect it to: Your baby begins life with fragmented sleep and frequent feedings. Virtually every parent is prepared for disrupted sleep at this time. Over the course of the first few months or so, the interplay between sleep and the three waking factors are intuitive. As you get to know your baby, you start to learn when he or she will be sleepy, and you anticipate that need. As your baby needs less-frequent feedings, he or she will naturally start to sleep longer stretches during the day and at night. These stretches might start with three hours, but over the course of a few weeks, they grow to four hours, then five hours, and so on. Some lucky parents might even see their baby naturally sleep through the entire night during this time (10–12 hours straight!). This is a beautiful progression that feels very natural and appropriate.

Unfortunately, Mother Nature is quite the saboteur, and somewhere around 3–4 months everything changes. Everything. Around this time, sleep matures. So, instead of sleep being a constant state, it becomes dynamic, and your baby will start to go through different types of sleep, called sleep stages. Sleep stages follow a predictable order that flow together in sleep cycles. These sleep cycles last about 60–90 minutes during the night (sometimes 120 minutes as they are developing) and are marked by a brief waking that happens at the end of the cycle. This brief waking is the cause of most “sleep problems.

This waking is meant to be protective (adults have it too). It allows your baby to briefly check in with the environment and ask, “Am I ok?” When we fall asleep, we expect our conditions to remain constant throughout the night, so if your baby has fallen asleep in your arms and you then transferred him or her to the crib, the crib will feel wrong when he/she hits the checking wake-up. This means that after every sleep cycle, your baby will probably wake up, and you can interpret his or her cries as, “Hey, Mom! Dad! Something is wrong here!”

If you don’t know that this sleep “regression” is coming, then you’ll probably do what you normally do when your baby wakes up: feed him or her. Since that’s how your baby knows how to go to sleep, he/she will fall back asleep for another hour or two and then wake again. and you’ll feed him/her again. After a few nights of this, you’ll convince yourself that this is a growth spurt or teething or your child getting sick, but the waking usually doesn’t resolve on its own (hence why “regression” is the wrong term). At this point you’ll have reinforced that feeding is the way to get to sleep, and your baby will have started to take in more calories during the night. This means that the wakings now have a dual nature: 1) your baby is waking due to the sleep association, but 2) he or she is also now genuinely hungry at night. Many babies get stuck in this reversed feeding pattern, because another change that happens around 4 months of age is that most babies become very interested in the world around them and become very distracted during daytime feedings. This reduction in daytime feeding paired with increased night feeding means that you’re stuck in a pattern that can be difficult to fix.

What Can Be Done About This?

If your baby is younger than 3–4 months and hasn’t yet had a sleep regression, then the best thing you can do is give your baby practice falling asleep in the place where you would like him or her to sleep all night. Start a little nap and bedtime cue (e.g., singing a specific song, rocking, bouncing, comforting), and when your baby is tired, put him/her in the sleep space awake. Your baby may be confused and frustrated by this, and that’s fine; just pick him/her up and repeat your sleep cue. You can rock/nurse to sleep, or you can try to put him in the crib again, awake. At this point in a baby’s life, you shouldn’t try to force the crib if your baby isn’t ready to fall asleep there on his/her own, but you do want to teach him/her that the crib is a reasonable place to sleep. If your baby never even has the chance to fall asleep there, then there’s no reason he/she should accept the crib; from his/her perspective, in your arms is the right place to sleep. In little babies it’s all about offering the chance; you don’t have to do it every day or at every sleep bout, but it is important to think about this and start to make change in anticipation of the four-month regression.

You certainly don’t want to deny your baby feedings when he or she is hungry. It can be really difficult to disentangle true feeding needs from sleep associations, but it can be done if you pay close attention to your baby’s pattern. If your baby normally sleeps 7:00pm–1:00am, eats and then sleeps 1:00am–4:00am, eats and then sleeps until 6:00am, then you have a good sense of his or her true needs. If one day, somewhere between the 3 to 4 month mark, he or she is up at 1:00 am and 2:30am, you can begin to suspect that this might be the beginning of the “regression.” If your baby hasn’t suddenly increased daytime feeding (which would indicate a growth spurt), then it’s probably the regression creeping in on you. Since you can feel pretty confident that your baby doesn’t need to eat at both 1:00am and 2:30am, this would be a good time to teach your baby to go back to sleep in new ways. For example, feed him or her at 1:00am as usual, then at 2:30 simply rock, bounce or hold him/her until he/she goes back to sleep, rather than feeding. The goals are to teach your baby that there isn’t just one way to fall asleep, and to keep nighttime calorie intake stable. The rocking can also become a sleep association, so if your baby continues to wake up and isn’t hungry, but wants to be rocked to sleep, use the suggestions above to teach him or her that the crib is a reasonable place to be (offer the sleep cue, put baby in the crib awake, pick baby up and offer the sleep cue, put baby in the crib awake, etc.).

If your baby is going through the 3–4 month sleep regression, then you need to evaluate the extent of the problem. Is your baby really eating a lot more at night than before the regression? Is he or she eating a lot less during the day? If so, then you will need to taper feedings at night before doing anything else (see our blog post and webinar on gentle ways to reduce night feeding). If your baby is truly hungry, then you don’t want to ask him or her to go back to sleep. He/she will be frustrated and so will you. First, determine how long your baby eats (or how many ounces he/she is taking if bottle feeding) and just reduce “extra” feedings a little each night. During the day, make sure you feed your baby in a quiet, distraction-free environment in order to ensure he/she gets nice full feedings. Consider cluster feeding at the end of the day in order to ensure he or she has had ample opportunity to eat as bedtime approaches. Once your baby is eating just a tiny bit or for a very short duration, you can start rocking him or her through those extra wakings rather than offering a feeding.

During this process, you will need to start putting your baby in the crib awake at bedtime (you can use the simple strategies that we described above). Also as mentioned above, some babies will develop a sleep association with rocking, so once you’ve reduced the “extra” feedings, you can start to break up the rocking by returning your baby to the crib awake. The suggestions that we outlined for “not yet regressed” babies will work to teach older babies to go back to sleep too. Depending on your baby’s age, you may be able to do something a little more structured at bedtime and during the night if you want the process to go faster. We generally don’t recommend really aggressive sleep training for babies going through this regression. We also don’t think there is one right way to do sleep training. You may opt for a fast approach, or you may opt for a very gradual adjustment. Your parenting style matters, as does your baby's personality. There are many ways to get to healthy sleep. Check out our thoughts on that here.

A Final Note: If your baby is able to put him- or herself to sleep at night and is still waking several times a night to eat, then it’s probably because his/her body is expecting calories at night now (the four-month regression led to an increase in nighttime calorie intake, and now they are “stuck” in that pattern). That said, sometimes a baby can fall asleep independently and have a sleep association hang on during the night. This is why sleep is so hard! There isn’t just one thing that causes trouble. Sleep problems are usually caused by complex layers of issues, and developmental changes such as the four-month regression cause new issues like extra night feedings. Please search our other blog topics to help with your problem solving.

The four-month regression can be prevented if you are aware that it’s coming and plan for it. If your baby has already gone through it and sleep is crazy as a result, then rest assured that life can go back to normal. We hope you find these suggestions helpful, but if you feel your situation warrants a more personalized plan, then book a consultation with us and we’ll help you through these tough times.