Cat naps, sleep regression, fighting sleep… Sounds like a 5-month-old sleep schedule! From wake windows to nap schedules, here’s the low-down. At 5 months old, your baby is going through a real transitional phase, so trying to stick to a strict 5-month-old sleep schedule won’t work for a lot of babies. Maybe learning to roll is playing havoc with overnight sleep, or the four-month developmental progression (or sleep regression as it’s often referred to) is lingering on.