Thursday, April 1, 2010

The Science of Infant Sleep Part II: Big Changes in Sleep Patterns (6 to 16 weeks)

The first 6 weeks are finally over! New parents, give yourselves a big "high five!" You are probably noticing that things already seem a little easier. At least, you are more familiar with your babies’ needs and cues and likely to be getting a little more sleep than you were at first. In this post, we’ll share information about some of the changes your baby will go through from 6 to 16 weeks and how these changes might affect how your baby sleeps.

Six to Twelve Weeks

While you’ve been waking up several times at night to feed, diaper, and console your baby, his little body has been going through a lot of development. His body and his tummy have grown and expanded, allowing him to take in more at each feed. He still falls asleep dreaming (remember to look for those eye movements and body twitches), but he spends less and less time in the “active sleep” state after he falls asleep. That means that you won’t have to wait so long to put him down if he is sensitive to position changes when he is dreaming. Just a few minutes should do it! His body also has started to make and use hormones like melatonin and cortisol to help him develop and follow his own circadian rhythms. When he is sleeping, you’ll notice that your baby won't move as much or make as many little noises as he did when he was younger. You probably won't find swaddling to be useful anymore and you will be less likely to be awakened by his quieter late-night stirrings. He’ll start to sleep longer stretches and concentrate that sleep at night but be prepared to get up with him, because he still will be likely to need a nighttime feeding or two.

While all babies wake frequently in the first 6 weeks, some babies start sleeping longer (5 to 6 hours) by the time they are 3 months old; others do not. This period of transition can be very confusing because 3-month-old babies sometimes sleep for longer periods and parents may assume that their babies should always sleep that way. Your baby will show progress toward sleeping longer stretches, but this progress is often of the “one step forward, two steps back” variety as babies hit growth spurts or have other reasons for waking. Around 3 months, parents will start getting pressure from family, friends, and even strangers suggesting that “it’s about time” that their babies should sleep through the night even though most babies don't do so consistently until much later.

Twelve to Sixteen Weeks

Big changes happen as babies get closer to 4 months of age. Most babies start falling asleep in quiet sleep (like their parents) by the time they reach 4 months. This means that they will drift off and stay asleep even when put down right away for nap or nighttime. Babies will also be working hard at developing their “self-soothing” abilities both when they are awake, like sucking on their fingers when they are upset, and at night, by going back to sleep without crying when they wake for a few moments during the night. As with any aspect of being human, there is a great deal of variation in babies’ self soothing skills. Some parents of 4-month-olds are relieved to be sleeping for much longer stretches and other parents with waking babies are wondering what they are "doing wrong." By 4 months, the pressure is really on to reach the ultimate parenting nirvana of sleeping through the night.

Sleep-deprived parents will adopt a wide range of strategies to get more sleep including the use of sleep training methods, co-sleeping, feeding strategies (like weaning from the breast or adding cereal to baby’s bottle against the doctors’ advice), or tag-team efforts for nighttime care. Many parents are willing to try nearly anything to get more rest. Some parents seek advice from parents who claim to have “good sleepers,” hoping to find some answers. Others find that they get advice from everyone whether they want it or not. We have already learned how passionate folks can be about their efforts to get babies to sleep longer. Rather than making any attempt to prescribe the “best way” to get babies to sleep more like their parents, we’ll share (next time) what science tells us about how baby and family characteristics interact to contribute to differences in how babies sleep.

Next time: The Science of Infant Sleep Part III. The Sleeping Relationship


  1. Can't wait for the next installment!

  2. I was surprised to read that the need to swaddle should end so early. I've never read anything suggesting it so soon, and I've talked to parents who have swaddled until their babies were almost a year old! My own 12 week old is a great sleeper, but whenever she's unswaddled she hits herself in the face until she's back awake.

  3. Interested in a post on baby wearing and baby carrying. What are the best products (ergo vs. baby bjorn; back vs. front carrying) based on age (newborn, infant, toddler)?

  4. For the first 6 weeks we swaddled our son in the hospital blankets but as he's gotten longer and stronger, we have had to use swaddle products like Kiddopotomus and the Miracle Blanket.

    If he sleeps on us he does not need the swaddle but if he sleeps on his own, the swaddle keeps him from waking himself with his movements. He wakes up when he's hungry, swaddled or not!

  5. Yeah my son needed to be swaddled till he was almost 6 months. If we'd had larger swaddlers we probably would have kept doing it... Of course he didn't sleep more than 3 hours at a time until 9 or 10 months either....and that was with a lot of (gentle)help....

  6. Thank you for the interesting information. I'm not sure how "sleeping through the night" became the lynchpin of good parenting, but this blog's attitude of education and understanding is a breath of fresh air!

  7. Regarding swaddling: our doctor recommended stopping at 4 weeks because she could break out of it and risk suffocation.

  8. Swaddling is not even a common practice in our country. We only swaddled the child until a month old. I don't know if which is better. But for my toddler, it works just fine.
    By the way, this article is great. It helps parents like us understand how our babies behave.
    Thanks and will be waiting for the next article!

  9. We are wondering why our son really likes toys that make squeaky sounds such as Sofie the Giraffe and Alex Jr. Squeezy Squeakies.