Why your baby suddenly stopped sleeping through the night (and how to fix it)

If your baby is suddenly waking more often at night, or suddenly they'll only sleep on you, you're probably wondering what has happened to your sleepy newborn... When this happens and your little one is 3-5 months old, it usually means your baby is going through what's known as the 4 month sleep regression. This sleep regression is totally normal. It's not just a phase.