Around four months, many parents feel as if sleep has suddenly disappeared. A baby who once slept in longer stretches may begin waking every 45 minutes. Naps become short. Bedtime feels more fragile. The transfer from arms to crib becomes almost impossible.
It can feel like something went wrong, but this stage is usually a sign of development, not failure.
Around this age, a baby's sleep begins to mature. Instead of staying in simpler newborn sleep patterns, they begin moving through lighter and deeper sleep cycles. During those lighter moments, many babies wake fully and need help settling again.
The most supportive thing parents can do is create consistency. A simple bedtime rhythm can help baby understand what comes next. Bath, pajamas, feed, book, sound machine, sleep. The exact routine matters less than the repetition.
An earlier bedtime can also help. When babies are overtired, they often wake more, not less. A calm evening routine that begins before baby is frantic can make the whole night softer.
The room matters too. Darkness and steady sound can reduce the little disruptions that wake a baby between cycles. A sound machine, blackout curtains, and a familiar sleep sack can all become cues that sleep is coming.
This is also a season where parents can pause briefly before rushing in. Sometimes baby is stirring between cycles rather than fully awake. A short pause gives them a chance to resettle. If they need comfort, you can still go in. The point is not to ignore them. It is to give sleep a little space to reconnect.
The 4-month transition can feel endless when you are inside it. But for most families, it is a phase. With gentle consistency, many babies begin linking sleep cycles more smoothly over the following weeks.
A hard night does not mean you are doing it wrong. It may simply mean your baby is learning a new way to sleep.