
A baby's birth weight is an important indicator of their health. The average weight for a full-term baby is around 7 lbs (3.2 kg). Newborns are measured in terms of weight, length, and head circumference, with the latter being important for monitoring brain growth. The average newborn is about 50 cm or 19 3/4 inches long, with an average head circumference of 35 cm.
What You'll Learn
Average newborn weight
A baby's birth weight is an important indicator of their health. The average weight for a full-term baby (born between 37 and 41 weeks of gestation) is around 7 pounds (approximately 3.2 kg). Generally, smaller and larger babies are more likely to experience health problems.
Newborns may lose as much as 10% of their birth weight in the first few days after birth. This means that a baby weighing 7 pounds 3 ounces at birth might lose up to 10 ounces in the initial period after birth.
Babies are weighed daily in the nursery to assess their growth, fluid intake, and nutrition needs. Your newborn will be weighed at the hospital and during all subsequent check-ups. Metric units are typically used to record a baby's weight.
The World Health Organization (WHO) publishes standard infant growth charts based on the expected growth of children in six countries, including the United States, in optimal growth environments. These charts are used by healthcare providers to monitor a baby's overall health and development.
It is important to remember that every baby grows at their own pace, and there is a wide range of healthy birth weights. A doctor will assess how closely they need to monitor a baby's growth over time.
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Average newborn length
The average newborn baby measures about 50 cm or 19 3/4 inches long from the top of the head to the heel of the foot. This measurement is called recumbent length and is taken with the baby lying down. Doctors consider a range of 18.5–20.9 in (47–53 cm) to be typical.
Male babies are, on average, slightly longer than female babies. A newborn's length can be predicted by doubling the length of the baby's head and adding 10 cm. For example, a baby with a head circumference of 35 cm is expected to be about 45.7 cm or 18 inches long.
Babies grow quickly and typically gain about 50% in length during their first year. They are usually measured at regular check-ups during their first year, and these measurements help healthcare providers monitor the baby's overall health and development.
While it's important to track a baby's growth, it's also crucial to remember that every baby grows at their own pace. There is a wide range of healthy sizes, and factors such as genetics, environmental influences, nutrition, activity levels, and health conditions can impact a child's growth.
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Average newborn head circumference
The average newborn head circumference is about 13.47 inches (34.2 cm) for a baby born between 37 and 41 weeks of gestation. This measurement is also known as the fronto-occipital circumference (OFC) and is a good indication of a baby's brain development. It is an important measurement for well-baby health care as it shows the development of the central nervous system. Boys tend to have slightly larger heads, but the difference is usually less than half an inch (1 cm).
The head circumference of a newborn is usually about half the baby's body length in centimetres, plus 10 cm. So, for example, if a baby is 18 inches long, that's 45.7 centimetres (18 x 2.54), and their head circumference would be about 32.9 cm, or a little under 13 inches.
The first measurement of a baby's head circumference is taken shortly after birth, and measurements are then taken at every well-baby and well-child visit up to 2 years of age. This is because the growth of a baby's head during this time shows the development of their brain. By age 3, the brain is 80% of its adult size.
If a baby's head circumference is outside the normal range for their age and sex, a healthcare provider will want to check for problems. If a baby's head is much smaller than average, it may be a sign that their brain has stopped growing or isn't growing properly, which could be due to an infection or a genetic condition. If a baby's head is much larger than average, it may be a sign of hydrocephalus, a rare condition that causes a buildup of fluid in and around the brain, increasing the pressure in the head.
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Average newborn abdominal circumference
The abdominal circumference of a newborn is the distance measured around their abdomen. This is one of several measurements taken to assess a newborn's health, along with weight, length, and head circumference.
Abdominal circumference is not routinely measured and no reference values have been established for this measurement. However, it is necessary to measure abdominal circumference to ascertain the size of the abdominal viscera in healthy newborns and to objectively determine and specify the abdominal circumference in patients with abdominal pathologies such as necrotizing enterocolitis (NEC) and other diseases of the abdominal cavity.
One study found that the average abdominal circumference of 220 premature newborns was not influenced by the sex of the newborn. The study also found a positive correlation between abdominal circumference and birth weight. Birth weight can be used to estimate the normal abdominal circumference in unfed preterm infants.
Another study of 373 newborns with a mean gestational age of 31 weeks and a mean birth weight of 1,540 g found that the median abdominal circumference was 27.0 cm. The study also found that the abdominal circumference to head circumference (AC/HC) ratio was 0.91 in the absence of abdominal distention, and higher in cases of abdominal distention and NEC.
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Metric conversions for newborn measurements
Weight
The average weight of a newborn baby is around 7 to 7.5 pounds (lb), or approximately 3.2 to 3.4 kilograms (kg). This can be converted to grams (g) as follows:
1 lb = 453.59237 g
Therefore, the average weight of a newborn baby in grams is around 3,215 g to 3,447 g.
Length
The average length of a newborn baby is approximately 19.5 inches, or around 49.5 centimetres (cm). This can be converted from inches to cm using the following conversion rate:
1 inch = 2.54 cm
Therefore, the average length of a newborn baby in cm is approximately 49.5 cm, with girls measuring around 49.2 cm and boys measuring around 49.9 cm.
Head Circumference
The average head circumference of a newborn is around 13 3/4 inches, or roughly 35 cm. This can be converted to cm using the same conversion rate as above:
1 inch = 2.54 cm
Therefore, the average head circumference of a newborn in cm is approximately 34.9 cm.
Abdominal Circumference
The abdominal circumference of a newborn is the distance around their abdomen. This measurement is not provided in the sources. However, it can be estimated based on the average newborn length of 49.5 cm. Assuming the newborn is roughly cylindrical in shape, the abdominal circumference can be calculated as:
2 * π * radius = circumference
Using the formula, the abdominal circumference can be estimated to be approximately 31.8 cm, or 12.5 inches.
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Frequently asked questions
The average weight for full-term babies (born between 37 and 41 weeks gestation) is about 7 lbs (3.2 kg). Newborn babies may lose as much as 10% of their birth weight in the first few days.
The average newborn is about 50 cm or 19 3/4 in long, measured from the top of the head to the heel of the foot. Doctors consider a range of 18.5–20.9 in (47–53 cm) to be typical.
The average newborn's head measures 13 3/4 in (35 cm). Generally, a newborn's head is about half the baby's body length in cm plus 10 cm.