Why does your baby fight sleep during nap time or at night? Babies haven’t fully developed their circadian rhythms yet, which is why they often have erratic sleep patterns. This is one of the most formative times in their lives and creating a circadian rhythm is crucial to their development. Parents often find themselves trying everything in the book to establish a consistent sleep schedule for their little ones. By understanding light and the circadian rhythm, you can help your baby find their ideal sleep schedule.