Uzm. Dr. Hasan Keleş- September 8, 2026
- 2 min read
- Growth and Development
- — reads
The fourth month brings a clear leap in motor skills. The baby no longer just watches their surroundings — they reach for them.
What to expect this month
Movement
- Rolling from back to side, and in some babies a full roll
- Pushing up with the arms on the tummy and lifting the chest well clear
- Reaching for an object and grasping it with the palm
- Bringing everything they grasp to the mouth
Social and language
- Laughing out loud
- Playing with their own voice and changing pitch
- Interest in their reflection in a mirror
- Beginning to tell a familiar face from an unfamiliar one
Feeding
It is still too early for solids. A baby looking at food or smacking their lips does not mean they are ready; these are a natural part of development. Breast milk only is advised for the first 6 months. Vitamin D is continued.
Sleep: the fourth-month regression
This month the structure of sleep changes and begins to resemble adult sleep. The result can be waking more often between stages. A baby who used to sleep well suddenly waking frequently at night is something most families experience in this period, and it is temporary. Not disrupting the routine is the approach that helps most.
This month's vaccinations
| Vaccine | Note |
|---|---|
| 6-in-1 (DTaP-IPV-Hib-HepB) | 2nd dose |
| Conjugate pneumococcal (PCV) | 2nd dose |
| Rotavirus | Optional, 2nd dose |
Safety once rolling starts
- Swaddling should be stopped
- The baby should never be left alone on a changing table, at the edge of a bed or on a sofa
- Continue placing them on their back to sleep
When to see a doctor
- If the baby never reaches for an object
- If the head cannot be held upright
- If there is no laughing and no sound at all
- If there is excessive stiffness or excessive floppiness in the legs
- If one side is used noticeably less than the other
Previous month: 3-month-old baby development · Next month: 5-month-old baby development
Frequently Asked Questions
No. The World Health Organization advises breast milk only for the first 6 months. Even if a baby shows interest in food, that does not mean they are ready for solids; the interest is a natural part of development.
The second dose of the 6-in-1 vaccine and of the conjugate pneumococcal vaccine are given this month. The second dose of the optional rotavirus vaccine is also given at this visit.
In this period the structure of sleep starts to resemble an adult's, and the baby wakes more often between sleep stages. This is why a baby who slept well before may suddenly wake frequently at night; it is usually temporary.
A baby who has started rolling should no longer be swaddled. Keep placing them on their back to sleep; there is no need to turn them back when they roll on their own. There should be no pillow or soft object in the cot.
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