What is the average length of a newborn?

The length of your baby in the first year of birth is an important determinant of health and vital physical characteristics. Pediatricians continuously track the length of a baby from the first week to evaluate growth patterns in subsequent months. As a responsible parent, you should also keep an eye on the length of your baby and report any anomalies, if needed.

Often, length and height are used interchangeably. However, pediatricians may record these differently. For instance, the height is usually measured when we’re standing in an upright position. On the other hand, the length is measured while the baby is lying down. For babies, pediatricians will always record the length of a baby because it’s difficult to keep a baby in an upright position unless they grow up to stand on their own.

The length of a baby is measured from the top of their head to the bottom of their heels while they are lying down. It also makes sense to measure the length instead of trying to measure the height of a baby in an upright position.

While standing, the posture of a newborn will hinder any efforts to record the height; therefore, you should always record the length because a minor difference in the scale can cause miscommunication between you and the doctor.

What’s the Average Newborn Length in the United States?

The average newborn length of babies born the United States is 50cm. Still, the range of length varies from 45cm to 60cm depending on different physical characteristics. It’s also important to note that the average newborn length of babies may vary from one region to another; hence, it makes sense to compare the length of your child with the length of other children in your region.

If you’re in the United States, you should use a CDC scale to measure the length of a newborn. Every pediatrician has a CDC growth chart, which they use to track the health record of babies until the infant is two years old. The chart consists of a percentile curve illustrating the height, weight, and other body measurements. By looking at the chart, you can easily compare the average newborn length of babies in the United States with your baby.

Since early years are instrumental to the development of a baby, pediatricians regularly compare the length of a baby against average newborn length until the child is at least one year old. For premature babies, such evaluation may continue until the second birthday.

Boys vs. Girls

According to CDC classification, if the length of your baby is in the 50th percentile, it means that half of the babies are shorter than your baby and half of them are longer. In fact, the length of a baby differs among genders, which means that boys are usually longer than girls. From a parent’s perspective, you will measure the average newborn length against the gender of a baby.

At birth, the 50th percentile of boys is approximately 50cm long compared to girls who are 49.1cm long. The difference in the length of boys and girls starts to increase gradually. The average newborn length for boys in the 3rd month is 61.4cm, which is eighteen inches longer than their female counterpart.

By six months, 50th percentile length for male babies is 67.6cm compared to 65.7cm for female babies. The difference in length of both genders remains constant as they celebrate their first birthdays. After one year, the average newborn length for boys is 75.7cm against 74cm for female.

Growth of Babies in the First Year

During the first year, your doctor should keep you in the loop about the development of your baby. The length of your baby will generally increase at a faster rate in the first half of the year. A baby will grow in length by 1 to 2 cm every month. After six months, the growth will recede to 1 cm per month.

During the development, babies may face sudden growth spurt. These growth spurts cause a rapid increase in the length of a newborn during specific intervals. The first growth spurt starts as early as 10 days, which is followed by rapid development between 5 to 6 weeks. Changes in length are also more visible during the 3rd and 4th month.

As the body increases in length, you may also notice a behavior change in babies. Most babies will try to feed more often at irregular intervals. Similarly, they will become fussy waking up many times during the night. As a result, parents should be ready to cope with the situation because daily schedules may need to be adjusted accordingly.

When the average newborn length increases more rapidly, parents will definitely need larger clothes and diapers to accommodate the growth. The time and duration of growth spurt can vary among babies; therefore, you shouldn’t be overly concerned about these growth spurts. In fact, your pediatrician will keep a close eye on growth and development aspects of the baby.

Average Newborn Length in Premature Babies

A premature baby is a baby that is born before the normal 39 week gestation period. Depending on how early the baby is born, the length of the baby will also be shorter compared to a normal delivery.

To keep track of the length of a premature baby, doctors use a chart designed to compare the length of premature babies with other premature birth. For instance, if the baby is born 6 weeks premature, the pediatrician will not compare the baby with the normal delivery; instead, the average newborn length of a premature child is compared against the premature babies born 6 weeks prior to the normal delivery.

In this example, the baby will complete the birth cycle after six weeks, which is the normal time of delivery. From that particular point in time, doctors will also start comparing the length of the baby with other babies who had a normal delivery. Comparing the length of a premature baby with a normal baby is important because doctors want to keep an eye on the growth and development patterns.

After 2 years or 18 months, most premature babies catch up with other babies. This is also the time when you may predict the length of the baby as an adult. To get a rough idea of your baby’s future length, calculate the average length of both parents and add 5 inches for boys and subtract 5 inches for girls. Despite the fact that there is no scientific evidence to back up this theory, it will keep parents curious who are concerned about the height of their baby.

How important is Newborn Length?

The average newborn length is one of the important measures of development in a baby. Pediatricians will regularly check the length of a baby during every visit ensuring that there are no major anomalies. In fact, most doctors put more focus on the weight of the baby instead of worrying about the length.

It is assumed that the average newborn length will automatically increase as the baby gains weight. Proper diet and nutrition will help the child grow according to the genetic structure and environment. This is one of the reasons that CDC growth charts seen in pediatrician office combines the length and weight of a baby to provide an appropriate measure of development.

When to Be Concerned:

Under specific circumstances, it’s likely that the length of a newborn may not increase relative to the weight or other physical characteristics. If this happens, the doctor will check for specific symptoms to find a remedy. In rare cases, they may ask parents to test the baby for conditions such as hypothyroidism, growth hormone deficiency, and Turner syndrome, among others.

A responsible parent will always keep a close eye on the development of a baby. Besides measuring the average newborn length, parents must also ensure that their baby is meeting important developmental milestones. These milestones may include:

  • Social and emotional milestones: Responding to individuals by trying to look smile and looking at them.
  • Language and communication: Making sounds and trying to communicate with onlookers.
  • Cognitive skills: Following sound and the movement of things around them to interact with the environment.
  • Movement and physical development: Crawling and standing as the baby grows older.

Conclusion

All of these development milestones are checked every two months until the baby is at least five years old. Generally, you shouldn’t be too curious about the length unless there is a genuine reason to be alarmed. By focusing on the overall development aspects of the baby, you can better contribute to the health of your child.