1. The baby first learned to make a fist, then learned to pick up small objects and gradually controlled the movements of his hands.
2. By 6 months, if the baby wants to sit up, he can keep his head and back in a straight line when he gets up, and he will skillfully turn his head from left to right. So if the baby can do this, it means it is healthy.
3. At 7 months, the baby's head movements are bigger and more coordinated, and at 9 months, it hardly affects the body balance. All these indicate that the baby's spinal strength is constantly increasing.