It is not normal for a 4-month-old baby to not roll over, but a normal 3-month-old baby can roll over. 4 months old baby’s developmental standards are to be able to roll over on their own, grab toys, laugh out loud, play with their little hands and feet, and stare at strangers who come into the house. If your baby can’t roll over at 4 months, you should go to the pediatric neurology or child health department for a detailed neurological examination, and combine your baby’s birth history and growth history to see what causes your baby’s motor development to lag. At this point, regardless of the cause, rehabilitation is necessary. The rehabilitator will assess the baby’s status and treat him/her with the appropriate rehabilitation techniques. After the rehabilitation treatment, the baby will be evaluated every month, while rehabilitating, to see if the baby’s motor development can catch up with normal children of the same age, if the baby’s development catches up with normal children of the same age, it means there is no problem.