Healthy infants come in a range of sizes. But looking at the average growth, most babies have tripled their birth weights by the first birthday. Their heads have grown by about 4 to 5 inches (about 10 to 13 centimeters). And most babies grow about 9.5 inches (24 centimeters) longer in the first year.
But a baby's growth is not constant. It naturally comes in bursts. Nutrition affects how fast babies grow. And the genes a baby inherits also affect growth.
Generally, a baby's growth follows some basic guidelines for growth in the first year:
- Weight. Babies tend to gain weight fast and then slow down. In the first few months, babies gain about 1 ounce (28 grams) a day. That slows at around 4 months to about 20 grams a day. As they turn 6 months old, many babies are gaining about 10 grams or less a day.
- Height. From birth to about age 6 months, babies tend to grow about 1 inch (2.5 centimeters) a month. From ages 7 to 12 months, a baby might grow about half an inch (1.3 centimeters) each month.
- Head size. A baby's head size is measured to get an idea of how well the brain is growing. During the first month, a baby's head may increase about 1 inch (2.5 centimeters). But on average, the skull grows about 0.4 inches (1 centimeter) each month.
Your baby's health care provider will track growth at well-baby exams. The provider will likely mark your baby's growth on a standard growth chart. If your child has a condition that affects growth, the provider can use a chart specifically for that condition.
The provider is looking for steady growth along your baby's personal growth path.
Your baby's place on the curve of a growth chart may not be as important as the trend of the curve overall. Checking body measurements at each visit helps you get an idea of what to expect in the future. It also helps you and your provider see any delays or shifts that might need closer attention.