While newborns vary in size and shape as much as adults do, full-term babies tend, on average, to weigh between 5 pounds, 11 ounces and 8 pounds, 6 ounces. They're usually between 19 and 21 inches long, with a head circumference of about 13 1/2 inches.
Your baby is more likely to be on the larger side at birth if:
- You and your partner are larger than average
- Your baby is a boy
- You developed gestational diabetes during pregnancy
- Your baby was overdue
Your baby is more likely to be on the smaller side at birth if:
- You and your partner are smaller than average
- Your baby is a girl
- You suffered from high blood pressure or asthma during pregnancy
- You had poor nutrition habits during pregnancy
- You smoked, drank, or used drugs during pregnancy
- You gave birth to multiples
As you can see, there are many contributors to birth size. Thus, it's not possible to accurately predict childhood or adult size from how big or small your baby was at birth. A tiny newborn won't necessarily be a petite adult, and a large baby isn't guaranteed to grow up to be a football player.
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.
When Growth Patterns Change
Typically, babies establish a steady growth pattern within the first six months of life. But occasionally, a baby's growth may deviate from its formerly steady pattern. For example, a baby who has been in the 80th percentile for weight may drop to the 65th percentile as of his most recent checkup. Although "falling off the curve" can potentially be the sign of a health problem, most often the change is not call for alarm.
Assuming your child is otherwise healthy, the drop in percentile could just mean that your baby's weight or height is adjusting to his intended genetic size. For example, a baby who was born quite small because of various influences in the womb may shift growth curves during his first 18 months of life to match the percentile of his relatively large parents.
Besides genetics, your baby's activity level can cause a slowdown in her weight gain. A baby who has just begun crawling, cruising, or walking will burn many more calories than a young infant who spends the bulk of her time sitting in one place. Moreover, a baby who has realized her capacity to explore the wonders of the world may find herself too distracted to stop and eat!
Last, illness has the potential to reduce your baby's weight and change her growth pattern temporarily. Fever or a period of diarrhea and/or vomiting can cause a baby to lose fluid, and her weight may decrease. However, generally, a mild illness like a cold will not impact a baby's overall growth rate.
Of course, although most shifts in a child's growth pattern can be explained by normal life changes, you should always tell your pediatrician about any concerns regarding your child's development. If there's no obvious reason for the change, she'll want to evaluate things further.
Detecting a Problem
If your pediatrician is concerned about a change in your baby's growth pattern, she will ask you about your child's feeding habits and how many calories she takes in a day to make sure that your child is eating enough. In addition, your doctor will ask if your baby is hitting her developmental milestones, and about any recent illnesses and other behavior and social conditions. She will examine the baby, looking for a sign of a physical problem that may be a clue to the cause of, say, a large drop in baby's weight percentile. Based on the checkup, the physician may decide to do blood or urine tests, which can detect problems including low blood count, diabetes, and kidney disease -- all of which may affect a child's growth.
The growth and development of their baby is an area of both great excitement and concern for parents. Keeping informed, taking baby to his well-baby visits, and working closely with your pediatrician are the first steps to walking assuredly through these amazing times of change.
Copyright © 2003 AmericanBaby.com.
All content here, including advice from doctors and other health professionals, should be considered as opinion only. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.