Between one and four months, your baby will continue to grow at the same rate as during the first weeks of life.
In general, babies gain 1 1⁄2 to 2 pounds (0.7 to 0.9 kg) and grow 1 to 1 1⁄2 inches (2.5 to 4 cm). Your head circumference will increase by about 1/2 inch (1.25 cm) per month. These figures are average; however, they help measure your child’s development.
By two months of age, the soft parts of your baby’s head will remain open and flat, but by two to three months, the soft parts at the back of the head will close. Also, its head is likely to be proportionally larger than its body, because it grows faster. This is normal; their body will grow soon.
At two months of age, their baby will look round and plump, but as he begins to use his arms and legs more actively, his muscles will develop.
The bones will also grow rapidly, their arms and legs will straighten, and the body and limbs will appear to stretch, making your baby look taller and slimmer.