The Basics of Your Growing Baby

The first 12 months of your baby's life is a period of amazing growth. By the time he smushes his face into his first birthday cake, he'll have tripled his birth weight and grown about 10 inches. This development may be hard to notice on a day-to-day basis. But you'll see the proof at his well-baby checkups. "Your doctor will closely monitor your infant's weight, height, and head circumference this year to make sure he's growing at a healthy rate," says Parents advisor Jennifer Shu, MD, a pediatrician and coauthor of Heading Home with Your Newborn: From Birth to Reality. You, meanwhile, will probably have questions about how your child's doing and how she compares with other babies her age.

You'll remember your baby's birth weight forever, but in reality it's temporary: Newborns lose up to 10 percent of their weight in the first several days. After that, a healthy infant will gain half an ounce a day (a pound or so a month) for the first six months, then she'll slow down a bit. Preterm babies grow more slowly and don't catch up until age 2. Initially, breastfed infants may not put on weight quite as quickly as formula-fed ones. "Many women produce very little milk when they start nursing, but it's okay because early milk is rich and babies arrive with fat reserves to hold them over," says Dr. Shu. If your doctor thinks your baby isn't gaining at a good rate, she may weigh her before and after a feeding. If she's not getting enough to eat, you may need to give her supplemental formula.

At each checkup, your pediatrician will plot your baby's statistics on growth charts that assess how he compares with other kids. (An infant who's in the 15th percentile for weight, for example, is heavier than 15 percent of babies the same age.) "Some parents view growth charts as if they were grades in school -- they want their children to fall above the 90th percentile. You shouldn't think of them that way, though" says James McCord, MD, medical director of the pediatrics clinic at Children's Hospitals and Clinics of Minnesota, in St. Paul. Babies, like adults, come in all sizes, and there is a wide range of normal. What pediatricians look for is whether a child stays around the same percentile from one visit to another, not where he is on the curve.

You should expect your baby to be rounder by the middle of her first year -- she's probably got the feeding thing down but hasn't started moving much. Once she begins to crawl, she'll probably thin out, says Atlanta pediatrician Kirsten Mekelburg, MD. But if your child's weight is creeping up the charts while her height stays at the same percentile, it could be a cause for concern. A new study published in Pediatrics found that children whose weight gain outpaces gains in length in the first six months have a 40 percent risk of being obese by the time they're 3. In that case, the pediatrician may suggest that you watch her portions and that you make sure you're giving her food for nutrition, not comfort.

Your baby may be going through a growth spurt, which pediatricians say some, but not all, babies have. "I see spurts at roughly 2 weeks, 6 weeks, and again around 4 months," says Dr. Shu. Signs to look for: Your baby's appetite is insatiable, he's fussier than usual, and he wakes up more often for feedings. "You might also notice that he takes longer naps during the day to make up for the sleep he's losing at night." After all, sleep is absolutely essential for growth; studies show that babies release 80 percent of growth hormone during sleep.

A common question pediatricians hear: Does an infant's size have any bearing on her adult stature? The answer, in most cases, is no. Several factors affect a person's ultimate height, including nutrition, health habits, and, of course, genetics. "Tall parents tend to produce tall kids, and short parents have small kids," says Dr. McCord. "If one parent is tall and the other one's short, all bets are off." So who knows? Your tiny infant could very well grow up to be a statuesque adult.

An infant's head grows 4 to 5 inches in circumference during the first year. As with babies' other stats, there's a lot of variation in size, but what doctors look for is a steady increase. "Head circumference is a pretty fair indicator of brain growth," says Dr. McCord. "The main thing that makes the head get bigger is the brain growing under it." Tracking head size lets doctors know nothing's hindering brain growth, such as fluid buildup or premature closure of the skull bones (a condition that requires surgery to correct).

Originally published in the July issue of Parents magazine.