Leap 4 (Weeks 15–19): The Longer Fussy Stretch Around Four Months
For general reference only, not medical advice. Every baby develops at their own pace. If you are worried about your baby, contact a doctor or other health professional.
The window around four months is often the one parents remember most. It tends to last longer than the earlier ones, and it frequently overlaps with what is popularly called the four-month sleep regression: a baby who had started sleeping in longer stretches suddenly wakes more often again.
This page explains what is usually going on, why sleep often changes at this age, and how to get through it without feeling that you have undone all your earlier work.
Typical timing
The fourth window is usually placed at weeks 15 to 19 from the due date, so it can stretch across most of the fourth month. Babies born early tend to reach it later after birth, by roughly the number of weeks they arrived early.
Because the window is wide, many parents notice an unsettled week, a calmer week, and then another unsettled patch. That uneven pattern is normal.
What parents may notice
- More night waking after a period of longer sleep stretches.
- Shorter naps and fighting sleep even when clearly tired.
- Being easily distracted during feeds, especially in busy rooms.
- Rolling or trying to roll, sometimes in the crib at night.
- Wanting to be held, and crying when a familiar person leaves the room.
- Loud squeals, blowing raspberries and experimenting with their voice.
What is developing
Around four months babies become much more aware of their surroundings. They notice that events happen in a sequence, recognise familiar places and people more clearly, and react more strongly when something is new or different. Many start to roll, push up on straight arms during tummy time and reach for toys with more accuracy.
Sleep also matures at around this age. Babies begin to cycle through lighter and deeper stages of sleep in a more adult-like way, so they come close to waking several times a night. A baby who has always been fed or rocked to sleep may now need the same help to fall back asleep between cycles. This is a normal developmental change, not a step backwards.
Practical ways to help
- Keep a predictable order to the day: wake, feed, play, wind down, sleep. The order matters more than exact times.
- Start the bedtime routine a little earlier if your baby is getting overtired by evening.
- Offer some chances to fall asleep drowsy but awake, while still helping as much as your baby needs. Small steps are enough.
- Feed in a quiet, dim room when your baby is distracted, and offer an extra feed if a feed was cut short.
- Give plenty of supervised floor time so your baby can practise rolling during the day rather than mainly at night.
- Name people and objects in everyday moments, such as “Here’s Grandma” or “Bath time”, to support the sense of order your baby is building.
- Share the night load with another adult where possible, and nap when your baby naps if you can.
Sleep, feeding and safety
Once your baby shows signs of rolling, stop swaddling with arms in. A sleep bag with free arms is a safer option. Keep putting your baby down on their back. If they roll onto their tummy by themselves and can roll both ways, you usually do not need to turn them back, but the crib should stay clear of pillows, toys and loose bedding.
Many parents wonder whether to start solid food at this point. Most health organisations recommend starting solids at around six months, when a baby can sit with support and shows interest in food. A fussy phase alone is not a reason to start early. Talk to your doctor or health visitor if you are considering it.
When to consult a doctor
Speak to your doctor if your baby is not yet holding their head steady, does not follow moving objects with their eyes, does not make sounds or smile, or if feeds are falling and wet diapers are fewer than usual.
Night waking that comes with fever, ear pulling plus fever, coughing, breathing problems or vomiting is more likely to be an illness than a developmental phase. Get it checked rather than waiting.
Whatever the calendar says, seek urgent medical help for difficulty breathing, blue or very pale lips or skin, a baby who is unusually floppy or hard to wake, a seizure, a rash that does not fade when pressed, signs of dehydration such as very few wet diapers, repeated forceful vomiting, or a fever of 38°C (100.4°F) or higher in a baby under three months. Trust your instincts: if you feel something is wrong, contact a doctor or emergency service.