Many parents become concerned when their baby loses weight in the first few days of life. This is normal. Babies are born with extra body fluid that they lose over the first five days. They usually regain this weight during the following five days, so that by about day 10, they should be back to their original birth weight. Form that point on, most infants experience rapid growth.
At each well-baby visit, the pediatrician will track your baby's weight, height, and head circumference on a growth chart. This standard growth chart was developed from data using national surveys. Your pediatrician uses the chart to determine how your baby is growing compared with other babies of the same age and sex.
From birth to 1 month old, the average newborn gains 2/3 to 1 ounce a day and grows 1 to 1 1/2 inches in length.
In the next three months, babies usually gain 1 1/2 to 2 pounds and grow 1 to 1 1/2 inches each month. During this time, a baby may begin looking chubby; however as his activity level increases, those "baby rolls" will soon be replaced by developing muscle.
By 6 months of age, most babies will have doubled their birth weight.
By 12 months of age, most babies will have tripled their birth weight and will have grown 9 to 11 inches compared with their birth length.
By 24 months of age, most babies will have quadrupled their birth weight and will have grown 14 to 16 inches compared with their birth length.
In addition to measuring weight and height at well-baby visits, your pediatrician will measure the distance around your baby's head. This measurement, known as the head circumference, is used to gauge baby's brain growth. A baby's skull, and consequently her head, needs to increase in size to accommodate the growing brain. The soft spots on your baby's head, called fontanels, remain open in the first 18 months to allow for this expansion. In general, a newborn's head measures about 13 1/2 inches. Your baby will experience rapid head growth, particularly during the first four months, and by the end of the first year, her head circumference will be about 18 inches. She will add another inch in the second year, bring her head close to the adult size.
Whether you decide to breast- or bottlefeed will influence your baby's rate of growth in the beginning. Exclusively breastfed babies typically gain weight faster in the first two months of life compared with formula-fed babies. But these infants also tend to grow less rapidly than their formula-fed peers through about 1 year. Ultimately, however, neither breast- or formula-feeding has a long-term effect on a child's growth.
Parents are often concerned if their baby's measurements are near the high or low end of the growth chart. While such concerns are perfectly valid, it's important to keep in mind that one measurement neither predicts how your baby will grow nor does it necessarily suggest a growth problem. As long as your baby is growing steadily and consistently, there's usually nothing to worry about.