From months one through four, your baby will continue growing at the same rate they established during their first few weeks. Here's what you might expect.
In general, babies gain between 1.5 and 2 pounds (0.7 to 0.9 kg) and grow 1 to 1.5 inches (2.5 to 4 cm) each month during this period. Their head size will increase in circumference by about a half inch (1.25 cm) each month.
These figures are only averages, however, so keep track of your child's development as it compares to average growth charts.
At two months old, the soft spots (fontanels) on your baby's head should still be open and flat. But by three months, the one at the back should be closed. Also, their head is more likely to be proportionately larger as compared to their body because it grows faster. This is normal; their body will soon catch up.
Also at two months, your baby will look round and chubby. As they start using their arms and legs more actively, though, muscles will develop. Their bones also will grow rapidly, and as their arms and legs loosen up, their body and limbs will seem to stretch out, making them appear taller and leaner.
More information