What Influences Your Baby’s Growth?

Medically Reviewed by Louise Chang, MD on July 01, 2010
5 min read

A baby's first year is a time of incredible growth. In just the first six months of life, babies will double their birth weight. By the end of their first year, they'll triple their weight.

Most babies have their first well-baby visit within the first couple of weeks after they are born. Then they'll see the pediatrician again at two, four, six, nine, and 12 months. During these visits, the doctor will check the baby's growth. The baby's measurements will be plotted on a growth chart and tracked over time.

Most doctors use the growth charts established by the CDC. The CDC developed these charts by collecting measurements from thousands of American babies and children over time. Growth charts track three different measurements of baby growth: height, weight, and head circumference.

Growth charts make it easy for pediatricians to track a baby's development. "Babies come in all different sizes," says Joanne Cox, MD, associate chief of General Pediatrics at Children's Hospital Boston. "Growth charts allow you to evaluate in a very quick and easy way whether a baby is growing normally."

Here's how growth charts work: Doctors plot the baby's measurements on the chart to get a percentile. The percentile shows how the baby is growing compared to other babies of the same age and gender. For example, if a six-month-old girl is in the 25th weight percentile, it means that 25% of girls their age weigh the same or less than they do and 75% of girls their age weigh more.

Percentiles are a useful way to follow a baby's growth, but some parents get too caught up in worrying that their child is too high or low on the scale. Remember that growth charts are just a comparison -- they're not grades.

"It's not like you get an A+ if you're in the 100th percentile. It simply means this is where your child is compared to peers his own age," says Ari Brown, MD, FAAP, a pediatrician in Austin, Texas, and co-author of Baby 411 and Expecting 411."Really what we're most interested in is not the percentiles, but how your child is tracking to make sure that he's following his curve."

If your baby stays in the 15th percentile for both weight and height, it doesn't necessarily mean there's anything wrong. Your baby just might be smaller than other children of the same age.

Doctors start to investigate if a baby's height and weight measurements don't match up. For example, if the baby's weight is in the 50th percentile but their height is only in the 20th percentile, or their weight suddenly drops two or more percentile points, there could be a growth problem.

Plotting height and weight measurements on the growth chart helps your doctor determine whether your baby is growing normally and getting enough nutrition. Measuring head circumference shows the rate of head growth, which can be an indicator of brain development.

"If the baby's head isn't growing fast enough, then you worry that there was some kind of injury to the brain during birth, or the baby was born with some abnormality," Cox says. A small head could also be a sign that the bones of the skull have closed too early, leaving less room for the brain to grow.

When the head circumference is tracking larger than average, it could be due to fluid on the brain (hydrocephalus). Or, it could just mean that your baby has a large head. "Often, we'll measure the parents' head, because kids with large heads often have parents with large heads," Cox says.

More important than the size of a baby's head is how fast it’s growing. If the baby's head is getting larger than normal, the doctor might do an ultrasound to find out the cause of growth.

A premature baby isn't going to follow the same growth curve as a baby who was born full-term. Pediatricians will track a premature baby differently, or by using a special premature growth chart.

Preemies might start small, but eventually they catch up with their peers. "The first parameter that catches up is the head, and then the weight and height fall in after that, Brown says."

The typical newborn growth rate is about 1 1/2 pounds and 1 to 1 1/2 inches a month. Every baby grows at a slightly different pace, but babies who lag far behind or who are at the highest end on the growth chart curve will need close follow-up with a pediatrician.

Your pediatrician will evaluate a low-weight baby by asking about the baby's eating habits and general health. "You look at both what comes into the baby, and what comes out of the baby," Cox says.

Your pediatrician might ask you:

The doctor will check for any medical conditions that might be preventing your baby from eating enough. If your baby isn't growing because you're not producing enough milk, the pediatrician might recommend ways to increase your milk production, or have you supplement with formula.

Babies who are more than six months old can be started on solid foods. Brown recommends calorie-rich foods like eggs and whole-milk yogurt to improve weight gain.

It's rare for a breastfed baby to gain too much weight. Formula-fed babies who are putting on weight too quickly might need to have some adjustments made to their feeding schedule.

If you're keeping up with all of your well-baby visits, your pediatrician will make sure that your baby's growth is staying on track. In between visits, call the doctor if your baby:

  • Is refusing to eat or has trouble latching on if you're breastfeeding
  • Always seems hungry, even after feeding
  • Seems unusually sleepy or fussy
  • Throws up large amounts of milk or has diarrhea
  • Produces fewer than six wet diapers a day