It is not normal for a 3-month-old baby to have a soft neck, because the baby is rarely picked up at 3 months of age without the correct way of carrying and raising, and the baby can be held vertically for exercise, and the neck will be obviously stable after 1 week. If the baby is still soft and unstable at the age of 3 months even after the normal carrying, it is necessary to go to the pediatric rehabilitation department or the pediatric health department to find the cause of the developmental delay. Most of the brain injury or genetic metabolism, chromosomal lesions, mental retardation, etc. can cause developmental delay, so if the neck is still soft at 3 months of age, you should seek medical attention and give the necessary rehabilitation training.