Well you will be able to know this if you've tried extending the naps and despite your efforts it still hasn't worked and baby wakes up refreshed.
At 4 months, your baby should be able to sustain 2 hours of wakefulness. So, if you are doing less than that and baby is waking at the 45 min mark awake and alert, you can try extending her awake time by 15 minutes every few days until she is up to the 2 hour mark.
When you extend the awake time in 15 min increments, you are changing your EASY from a 3 hour to a 4 hour which is typical for most 4 month olds. If you are already there, and doing the 4 hour EASY with 45 min naps, you might try pre-empting the waking by:
Going in at the 35 min mark and waiting for the jolt. The beginning of the rise from deep sleep happens at about the 38 minute mark, so if you are there at the 35 you will catch it. Prepare to spend 20-45 mins in the room the first few times you do this. I started it today and it is already working. Get comfy, perhaps on a stool or standing by the crib and gently place your hands on your babys upper arms while she is swaddled. You are basically providing some pressure so that when/if she jolts, your pressure will prevent a startle awakening. If baby opens her eyes, use one hand to hold her arms and the other to shield her eyes with your hand. If the room is really dark you may be able to avoid the eye-part. Otherwise, maintain this position until baby falls back into deep sleep again. You will notice her breathing quicken when she comes out of sleep and she may grunt, life her legs and roll her head side to side. If you use a paci, you can insert it, but don't do so before she opens her mouth for it. Shoving a paci in there when not requested can actually wake her up more. Follow her cues for paci or out. You may put it in and she will close her eyes, rest and spit it out (keep holding her arms) and then suddenly seem like she needs it again - put it back and continue being careful not to let her come out of sleep due to jolts or wanting that paci - it can feel like a juggling act
The first time it may take her 20-30 mins to fall back into a deep sleep, but if you continue this for all naps, you will see that the time it takes her to fall back shortens and this means you will spend less and less time at the cribside.
We've been short napping for 5 weeks now and today had 3 naps of 1.5 hours each and a catnap of 45 min
I feel like I have my life back!
Now, if you do all of this and baby is still waking up at the 45, not going back, eyes pop open and yet she is alert and HAPPY, this is likely her biorythym. If she wakes up cranky then you know that she needs more sleep. You can, if you like, try for 10-15 mins to get her back to sleep and then if that fails, take her out, do quiet activity for another 10-15 mins or so and then you may notice her getting sleepy again - right back to sleep then!
Essentially, this will be a broken nap with some A time in the middle. It will then seem like EASASE in the cycle. You might do this for a while before you can get the *going in early* part to work, but then it can be smooth sailing!
Best of luck!
