1. Physical development indicators When a baby is 8 months old, his height is generally 68-75 cm and his weight is about 7-10 kg. Your baby\’s head and chest circumference will also increase at this time. The baby can now lift his head steadily and sit up with belly support. If you are worried about your baby\’s physical development, you can consult a pediatrician or undergo relevant examinations. 2. Cognitive development