Your baby's weight and height will be measured at every well-baby visit and compared to the normal ranges for babies of the same age. Keep in mind that all babies grow at different rates, so don't worry if your baby is a bit bigger or smaller than average.
Growth and weight gain
You will be told what percentile your baby is in for weight and height, compared with other babies of the same age. For example, if you are told that your baby is on the 90th percentile for weight, it means that they weigh more than 90% of babies their age.
Most healthy babies who are born full-term gain weight according to the following pattern:
| Age | Weight gain per day | Weight gain per month |
|---|---|---|
| One to three months | 30 g
(about 1 oz) | 900 g
(about 2 lbs) |
| Four to 12 months | 20 g
(about 0.7 oz) | 600 g (about 1 lb 5 oz) |
A useful rule of thumb is that most healthy, full-term newborn babies double their birth weight by four months and triple it by their first birthday.
Keep in mind, though, that all babies grow at their own pace. Your baby may gain weight faster or slower than the rates mentioned above. A small or large baby may be perfectly healthy. Also, babies have growth spurts and fluctuations in their rate of weight gain. Therefore, your baby might not remain at the same percentile for weight or height every time you bring them to the doctor for a well-baby visit.
If your baby was very large at birth, chances are that they will grow quite slowly for the first few months; by six to eight months, they will probably be close in weight to other babies their age. If your baby was small due to prematurity, they may catch up to normal weight over the first year of life.
The best way to keep track of your baby's growth and weight gain is to bring them to their regularly scheduled well-baby visits. their health-care provider will carefully measure and plot their weight, height, and head circumference over time, and will compare the measurements to standardized growth charts.
Here are some weight gain and growth charts for girls from the World Health Organization:
Here are a few weight gain and growth charts for boys from the World Health Organization:
Your baby's physician will utilize charts recommended for use in your region.
Although growth and weight gain rates can fluctuate, if your baby shows an inadequate rate of growth over time using the standard growth charts, it could mean there is a problem such as failure to thrive.
What is failure to thrive?
Failure to thrive is when any of the following occurs:
- weight less than the third percentile on a standard growth chart
- weight 20% below the ideal weight for height
- fall off from a previously established growth curve.
Babies who are failing to thrive should be carefully assessed to find a cause for their growth failure. They may need extra calories to catch up in their growth. These babies will also need to be followed closely by their paediatrician or family doctor.
Head circumference
Along with your baby's weight and height, their head circumference will be measured at every well-baby visit. Your health-care provider will measure around your baby's head at its largest area: above the eyebrows and ears, and around the back of the head. The measurement will be recorded and compared with their previous measurements, and with the normal ranges for babies of the same age. Head growth generally relates directly to brain growth.
If there is a problem with your baby's head growth, your doctor may become concerned about a possible problem. For example, an unusually large head, or one that is growing faster than normal, may mean that there is increased fluid within the skull. An exceptionally small head size, or one that is growing slower than normal, may mean that the brain is not developing properly.