Sleep regression is a common phase that many parents experience with their babies. It occurs when a baby's sleeping pattern is disrupted, resulting in frequent wake-ups at night and difficulty falling asleep. Although sleep regression can happen at any time during a baby's first year, it usually occurs around 4 months, 8-10 months, and again at 18 months. During these periods, there are several factors that can contribute to sleep regression, such as teething, developmental milestones, and changes in routine. Understanding when sleep regression occurs can help parents prepare for it and make adjustments to their baby's sleep schedule. With patience and persistence, parents can help their little ones get through sleep regression and back to a more restful sleep routine.