The Average Length and Weight of Newborns

If you're expecting a new addition to your family, get ready to pay attention to all sorts of measurements and statistics you would've never cared about before. This typically starts with counting the number of fingers and toes on your little one after they are given to you.

When all those numbers add up, the next question for most parents is: "How long is the baby and how much does she weigh?" That's because the weight and length of a newborn baby is among the most sought-after information when loved ones hear the news that a little one has been born.

While it's enjoyable to hear these vital statistics, weight and length are measured because they are valuable predictors of a newborn's health, and they also provide a suspected growth pattern to pediatricians. Keep in mind that averages indicate the most common weights and lengths for babies, and your baby may fall outside of these averages and still be completely healthy.

The Long and Short of It

The normal length of a newborn baby ranges from 18 inches to 22 inches, with the average being 20 inches. Being shorter or longer than the average length doesn't necessarily indicate a problem.

In fact, the height of the baby's parents can play a role in how long a baby is at birth. In other words, very tall parents might have a baby longer than the average, while shorter parents might have a baby that's smaller than average. However, concern for a smaller-than-average baby can come into play in the case of premature births.

A Weighty Issue

Newborn baby boy under a blue blanket

The Size of a Newborn Baby

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There is a wide range of what doctors consider a healthy weight for a newborn baby. Many factors contribute to the weight of a baby including the size of the parents, the mother's nutrition and age and prenatal care.

Most babies who are born full term (38 to 40 weeks gestation) weigh between 6 to 9 pounds, with the average full-term baby weighing in around 7.5 pounds. The averages are smaller for babies who are born prematurely and larger for babies born past 40 weeks.

Many health experts define low birth weight as less than 5 pounds 8 ounces at full-term, and larger than average is a birthweight over 8 pounds 13 ounces. Plus, boys are often larger than girls and first babies are usually lighter than siblings.

It's also important to remember that most babies lose about one-tenth of their birth weight during the first five days, then regain it over the next five, so that by about day ten they usually are back to their original birth weight.

What Does It Mean?

While there isn't as much concern when a baby is shorter or longer than average, being much lighter or much heavier may be cause for concern. Low birthweight babies are at a greater risk for oxygen deficiencies, infection, neurologic problems, difficulty feeding and difficulty maintaining body temperature.

On the other end of the spectrum, babies who are large for gestational age are at higher risk for a breathing problem called respiratory distress syndrome. They are also at a greater risk of experiencing birth injuries due to their size and they may have an excessive amount of red blood cells.