Remember, the body's natural sleep cycle is 45 minutes. Every 45 minutes, we "wake up" and transition into a deeper sleep state. This obviously isn't noticeable to you and I most of the time, or that would make for pretty horrible nighttime sleep! But to a baby who is just learning to sleep outside the womb, once they wake up at this 45 minute mark, they may or may not have the skills to fall back to sleep.
If you have established a flexible Babywise-like routine and baby has been napping well (at least 1-1.5 hours minimum), there are a couple of reasons baby may wake at the 45 minute mark. These reasons can include:
1) Growth spurts. Once your baby is on a flexible routine and napping well, you will definitely notice when a growth spurt comes along. The "biggest," most problematic ones seem to occur around 7-8 weeks and then again at 4 months. What happens is baby "wakes" at their 45 minute transition, realize they are starving to death, so they'll start to cry!
Solution: Feed baby! Babywise states that you always feed a hungry baby, even if it has not been 3 hours (or whatever you determine your feeding routine to be). Ensure baby takes a full-feeding. If he doesn't, there may be other reasons baby is waking. When baby wakes at 45 minutes, I would always try feeding first. If they don't take a full feeding, I know I need to troubleshoot elsewhere.
2) Fussy Period: Some babies go through a "fussy period." With Brooke we called it "cranky time." This usually crops up around 6 weeks and lasts a month or less. During this period, there could be several issues, but most of the time babies are just going through growing pains or nursing issues. It's not necessarily "colic" like everyone likes to label it. During the fussy period, baby will go through a rough sleep period.
Solution: Hang in there. Hold and comfort baby. Try using a swing or bouncy seat to help calm baby. Check your milk supply if you're nursing. Also, keep a log of foods you're eating to see if something may not be agreeing with baby. For instance, dairy, spicy foods, etc.
3) Noise: Some babies are light sleepers and sensitive to noise. Around 45 minutes is when we "wake" and go through a very light sleep state. We are most vulnerable to noise at this point. So baby is sleeping away and then goes through the 45 minute transition. At the same time, big sister decides this is the perfect moment to scream at the dog in the next room.....for a light sleeper, this will be a ruined nap. When I was first sleep training Will, who is a very light sleeper, I remember always telling Brooke to be super quiet around the 45 minute mark!!
If you haven't established a routine for baby, and baby has never slept for over an hour at a time, here is the problem:
4) Inadequate Sleep Skills: For the vast majority of moms (especially those whose babies are not on a flexible routine), this is the main reason for the 45 minute intruder. If babies are not taught early to soothe themselves back to sleep, the 45 minute intruder will most likely be with you for a very long time. Let me tell you, that you might love staring into your precious baby's eyes and seeing her coo 24 hours a day when they are about 8 weeks old, but when they're entering Terrible 2's, believe me, you are going to want more than a 45 minute nap out of them!! :) We've already talked about the importance of sleep for children. 45 minutes of napping per day is no where near adequate for a child until they are at least 4!
Solution: Sleep training--if your baby isn't a "natural sleeper," you need to ensure he becomes one. This can be done in a variety of ways including the 4-S Routine and of course the notorious CIO (Cry It Out). Cry It Out really sounds a lot worse than it really is! More to come on that :)