No one appreciates sleep more than a parent of a newborn or young infant. This is because sleep is a completely different experience in the first four months of life, from the way sleep is experienced the rest of one’s life. For all children 4 months of age and older, and all healthy adults, sleep is a well-regulated and incredibly necessary activity, that really does offer balm to the mind and help the mind think.
The pattern of sleep from ages 4 months and onward is defined by a very regular pattern of light sleep becoming deep sleep, then deep sleep becoming lighter sleep, moving into a phase of REM sleep (when most dreams occur), and then emerging from REM sleep at which point everyone gets to choose –wake up or do another cycle.
What Does a Typical Sleep Cycle Look Like?
The sleep cycle in a person 4 months of age and older goes as follows:
Stage I: A brief period that happens just as you fall asleep. This is a very light phase of sleep.
Stage II: This is a substantial phase of sleep, much deeper than Stage I, but not very deep. It is during Stage II sleep that memories of facts are deepened and organized.
Stages III and IV: These are the stages of deep sleep. It is hard to wake someone up during these stages. Their function is poorly understood, but they account for a large part of our sleep cycle. It is during Stage IV sleep that the familiar phenomena of sleep, sleep talking, sleep walking, sleep peeing (bedwetting), and night terrors take place.
REM: This is the stage in which the eyes dart back and forth, hence the name, Rapid Eye Movement. This is the stage most dreams occur, and so when most nightmares happen, too. It is thought this is the stage that memories of emotional events are deepened and organized. REM occurs on leaving Stage II and entering either Stage I or III, as noted above. People who sleep all night nearly always decide to do another sleep cycle when they end their REM period, and this happens about 3-5 times a night.
How is the Newborn Sleep Cycle Different?
Newborns and young infants don’t have these sleep cycles. Their sleep is divided into quiet and active phases. The quiet go on to develop into the four stages (I and II are light sleep, III and IV are deep sleep). The active phase goes on to develop into REM.
Newborns and young infants also sleep in short bursts between feedings. For the most part, they simply eat and sleep, eat and sleep. Add to that the fact that you never grow as rapidly as during the first four months of life. After birth, babies double their weight in five months! There is never another half a year in your life in which you double your weight.
Young babies also grow rapidly, gaining several inches in a few months. Again, there is no other time in your life you grow several inches in a few months. This dramatic rate of growing is visible, our newborns look much bigger a few months after birth. Dramatic growing demands dramatic eating, and newborns do just that.
It all makes a certain amount of sense that during the first four months of life when growing is at its maximum that feeding would be nearly constant, and sleep not yet developed into hours of nighttime sleep alternating with wakeful days. These facts provide all the explanation necessary to understand why all parents after birth experience a complete upheaval in their own sleep routines.
Why Babies Pivot at 4 Months
Some infants pivot before, but all healthy babies make a huge change in sleep abilities by four months of age. Two great changes are in place for all our babies by four months old:
- The first is that growing slows tremendously. No longer are our babies growing at an annual rate of 30-50 pounds and a foot a year (!). By age two, those rates drop to about 4-6 pounds and 2-2 ½ inches a year. The drop in these rates really begins to take effect by 4 months old.
- The second is that our baby’s brain develops a fully grown-up structure of sleep by 4 months old. By this age, an EEG will reveal our babies entering a nicely developed Stage 1 sleep when they fall asleep. Then they move along nicely to the deeper Stages (2, then 3, then 4), then slowing coming up to lighter sleep. Once up from Stage 4 to Stage 3 then Stage 2 sleep, we all move into REM sleep where most dreams occur. Now, here is the key point about sleep stages.
Whenever anyone from age 4 months old up comes out of REM sleep, they can choose to either wake up, or plunge back into another sleep cycle of deeper stages then lighter stages and REM again. All this sleep structure is in place for nearly everyone by the tender age of 4 months old. But no self-respecting 4 month old infant would ever tell their parents. Instead, they still look very much like the young infant who couldn’t put together 3-5 sleep cycles to sleep 6-12 hours straight through the night, and who needed to be fed 3-4 times a night.
What You Can Do
First things first. Forget about sleep the first four months. Your baby needs to eat and can’t sleep through at birth. But once you have put in your 4 months of sleepless nights, know that your infant can sleep all night, meaning 8-12 hours. They do not need any food overnight anymore, and their brains can handle sleeping without waking for that long of a stretch.
That means for the first 4 months you have few if any options. But from 4 months on, you do. You actually have only two options if your baby wakes up in the middle of the night after turning 4 months: respond, don’t respond.
Your baby will be fine either way, so you get to decide which you would prefer. Not responding leads to full nights sleep. Responding means you and your baby will be up however many times you respond each night. Now that you know what you can choose to do, and that you have a choice starting at 4 months, we wish you and your family all a cozy, pleasant night’s sleep.