The Reason Why Some Babies Take Longer To Sleep Through The Night

by Wendy Wisner
Originally Published: 
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Everyone says you forget the most difficult parts of early parenting, but I will never forget how awful sleep deprivation was. My babies were very frequent night-wakers, and they didn’t sleep all the way through the night for a very long time.

When my first child was a newborn, I spent many hours trying to figure out how to get him to sleep better (nothing worked), and I also spent a good deal of time blaming myself for a what a crappy sleeper he was. Every baby sleep book I read seemed to emphasize this as well: If your baby sleeps poorly, surely you (the mom) are doing something terribly wrong.

It wasn’t until I got myself to a breastfeeding support group and befriended a group of lovely moms (who also happened to have frequent night-wakers) that I learned some totally fascinating and important truths about baby sleep.

Basically, there is a reason why babies don’t sleep through the night – some for a very long time. And it has very little to do with what you are doing as a parent, but a whole lot to do with evolution, biology, and our often unrealistic modern expectations about infant sleep.

Let’s look at some of those facts, along with some of my favorite baby sleep experts’ opinions on the matter.

1. Blame the fourth trimester.

It turns out that humans are born probably a whole 9 months or so before they are ready. Think about other mammals: they come out walking and ready take on the world. Human come out as little helpless mushes (but so cute!).

Lots of experts believe that the first three months of a human baby’s life should be treated as a “fourth trimester” where the baby just needs a whole lot more coddling and TLC than most of us were led to believe. This also might be why newborns wake up so damn frequently at night.

Darcia Narvaez, professor of psychology at Notre Dame University, tells BuzzFeed News that a baby’s underdeveloped system is part of the reason they don’t sleep through the night for many months after birth.

“Human babies are born 9 to 18 months early compared to other animals,” Narvaez says. “So that means you want to keep that baby calm while the brain systems are finishing because they only have 25% of the adult brain-size developed, and a lot of systems haven’t set their thresholds and parameters yet.”

2. It’s evolution, baby!

Narvaez also blames evolution for the fact that babies are such light sleepers, citing the lifestyles of hunter-gatherers, who thrived on shorter sleep cycles. “It’s normal to have periods of waking up and short sleeps,” Narvaez explains to BuzzFeed. “With hunter-gatherers, they sleep for two hours and then they’re awake and that’s for the whole 24 hours.”

Another theory is that babies evolved to be wakeful at night so that their parents could keep vigil over them – you know, to guard them against dangers like wild animals and such.

“The evolutionary need to be vigilant during sleep and awaken quickly permitted early humans to adapt to changing social, psychological and emotional environmental challenges,” Dr. James J. McKenna — an anthropologist from the University of Notre Dame, and director of the Mother-Baby Behavioral Sleep Laboratory — tells HuffPost.

Peter Fleming, a professor from the University of Bristol, agrees, explaining to BuzzFeed News that for most of human history – and still in many parts of the world today – human babies were kept in close proximity to their parents, both during the day and during the night. And so babies have been programmed to expect constant human contact, even at night (as exhausting as it is!).

3. Your baby is trying to get your attention.

Your baby isn’t doing it to be a jerk, but part of the reason they are waking is because they want your attention – and maybe even because they miss you while you’re busy bustling about through the day.

“Typically, babies love sleeping during the day, and 6pm to midnight is the time they’re going to want to be awake the most,” Fleming says. “Actually, biologically that’s a big advantage because they will have more attention from their two primary caregivers at that time of day than at any other, because there are fewer distractions.”

Most babies outgrow the 6am to midnight parent-meet-and-greet within the first few months (thank GAWD), but that doesn’t mean they don’t still sometimes wake up just because they want a little extra attention and love from us.

4. It’s protective.

McKeena says that night-waking could actually save your baby’s life. According to McKeena, having several wakings a night may be protective to babies who are prone to sleep apnea, a potential cause of SIDS. When babies are in a deep sleep, they are less likely to rouse and catch their breaths.

“[W]e know that babies that die of Sudden Infant Death Syndrome (SIDS) likely had some kind of arousal deficiency (did not arouse sufficiently well enough),” McKeena writes in a paper for Evolution, Medicine, and Public Health. “Arousing is an infant’s best defense against a range of potential physiological challenges.”

In addition, says McKeena, who has studied mother/infant sleep extensively in his sleep lab, babies wake for emotional reassurance as well as for food. And when mothers respond it by hugging or touch, “we witness […] a suite of physiological changes including increased heart rate and higher oxygen levels measured by oximetry, all of which is remarkable to observe.”

5. Your baby is a genius.

OK, this one may be a bit of a stretch. But for parents of really wakeful babies (*raises hand*), we need all the vindication we can get.

As Fleming tells BuzzFeed, there is a correlation between “very high levels and development and intellectual achievement” and frequent night-waking. He even goes on to say that kids of parents who meet the needs of their wakeful babies have “greater empathy and more self-regulation, they have greater conscience, and one study showed they had more cognitive ability and less depression.”

Awesome. I’ll take what I can get.

Now listen: none of this is meant to minimize how extremely exhausting it is to have a baby who doesn’t sleep through the night. And if you are able to find a way to decrease night-waking that works for you and your baby, more power to you. But for those of us who are at our wits’ end with baby sleep and are apt to blame ourselves in some way for having a “bad” sleeper, it’s nice to know that actually, our baby is pretty normal – and possibly a freaking genius.

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