Growth and Your Newborn

Growth is a good indicator of general health, and babies who are progressing well are generally healthy, while poor growth can be a sign of a problem.

Growth and Your Newborn

In their first year, newborns grow in a big way, with most tripling their birth weights and increasing their lengths by about 50 percent.

From your baby’s first day, healthcare providers will keep track of weight, length and head size. Growth is a good indicator of general health, and babies who are progressing well are generally healthy, while poor growth can be a sign of a problem.

What Newborns Weigh

Just like adults, newborns come in a range of healthy sizes.

Most full-term babies weigh between 6 pounds, 2 ounces and 9 pounds, 2 ounces; average lengths range from 19 to 21 inches.

A newborn who is lighter or heavier than the average range is probably perfectly fine but might receive extra attention from doctors and nurses after delivery to make sure there are no problems.

A number of things can affect a baby’s size at birth. The length of the pregnancy is important. Babies born at their due date or later tend to be larger than those born earlier. Babies born prematurely are often smaller than full-term babies.

Other Factors Affecting Baby’s Size

Size of parents. Tall parents may have larger-than-average newborns; short parents may have smaller-than-average newborns.

Multiple births. If you’re having twins, triplets or more, you can count on your babies being relatively small. Multiples not only have to share their growing space in the uterus, they also are often born early, which leads to small size at birth.

Birth order. First babies are sometimes smaller than brothers or sisters born later.

Gender. Girls tend to be smaller, boys larger, but the differences are slight at birth.

Mother’s health during pregnancy. Factors that can lead to lower birth weights include a mother’s high blood pressure, heart problems, or use of cigarettes, alcohol or illegal drugs during pregnancy. If the mother has diabetes, the baby may have a higher birth weight. All conditions that can affect a baby’s weight should be closely monitored by the mother’s doctor. In addition, women should not smoke, drink alcohol or use illegal drugs during pregnancy.

Nutrition during pregnancy. Proper nutrition is essential for a baby’s growth in the uterus and beyond. A poor diet during pregnancy can affect how much a newborn weighs and how the infant grows.

Baby’s health. Medical problems, including some birth defects and certain infections acquired during the pregnancy, can affect a child’s birth weight and later growth.

Growth and Premature Babies

Premature babies generally are smaller and lighter than other newborns. A preemie’s weight will be largely determined by how early he or she was born.

Many pre-term babies are classified as having “low birth weight” or “very low birth weight.” In medical terms, “low birth weight” means a baby weighs less than 5 pounds, 8 ounces at birth. That’s the case for about one in every 13 babies in the United States, so it’s quite common. “Very low birth weight” means a baby weighs less than 3 pounds, 5 ounces.

Premature babies are given special medical attention immediately after birth, and a pediatric specialist called a neonatologist may be involved in their care. Many premature babies spend time in the neonatal intensive care unit (NICU) while they receive medical care, including feeding and observation of growth.

Is Bigger Better?

In the old days, a “strapping” baby with chubby cheeks and dimpled thighs was many people’s picture of a healthy newborn. But a baby born much larger than average may have special medical problems that need attention. Some exceptionally large babies, especially those born to mothers with diabetes, including gestational diabetes, may have problems for a few days keeping blood sugar levels up and may require extra feedings, or even intravenous glucose, to prevent those levels from falling too low.

How Newborns Grow

Babies are born with some extra fluid, so it is perfectly normal for a newborn to drop a few ounces when that fluid is lost in the first few days of life. A healthy newborn is expected to lose 7 to 10 percent of its birth weight, but should regain it by about two weeks after birth.

During the first month, most newborns continue to gain weight at a rate of at least 5 ounces a week. They generally grow in height about 1 to 1.5 inches during the first month. Many newborns go through a period of rapid growth when they are 7 to 10 days old and again at 3 and 6 weeks.

Should I Be Concerned?

Newborns are small, and it can be hard to know if your baby is gaining weight the way he or she should. You may worry that your baby has lost too much weight in the first few days or isn’t taking enough breast milk or formula. Most likely, everything is fine. If you are concerned at all, check with your doctor.

What’s Next?

Being small or large at birth doesn’t necessarily mean a baby will be small or large later in childhood or as an adult. Plenty of towering teenagers began life as small babies, and the biggest baby on the block can grow to be a petite adult.

By the time they’re adults, kids tend to resemble their parents in size. Genetics, as well as good nutrition and your attention, will play a large part in determining how your baby grows in the years to come.

Whether a baby starts out large, small or in between, in the first few months he or she can be expected to keep growing fast.