Normal birth weight and length

Updated April 17, 2017

Every parent of a newborn baby wants him to be as healthy as possible. A normal weight and length can be one of the first physical signs that a baby is healthy.

Normal weight

According to, most full-term babies weigh somewhere between 2.78 kg (6lb 2 oz) and 4.0814 kg (9 lbs 2 oz). If a newborn is lighter or heavier than normal, the medical staff may monitor them a little closer than a baby born at normal weight, just to be sure the baby is healthy.

Causes of abnormal weight

The health of the mother plays a large role in a baby's development and growth. Factors that can lead to a lower birth weight include a mother's high blood pressure; heart problems; or use of cigarettes, alcohol or drugs during the pregnancy. Also, a baby born to a mother who has diabetes may have a higher birth weight.

Normal length

According to, the average length of newborns ranges from 47.5 to 52.5 cm (19 to 21 inches). The length of the pregnancy has a big influence on the length of the baby. Logically, babies born on or later than their due date will usually be larger than those born earlier and babies born early are often smaller than normal.

Causes of abnormal length

As with abnormal weight, abnormalities that occur with height in newborns could also be caused by an unhealthy pregnancy, the influence of the parents' heights, the gestational age, nutrition during the pregnancy or birth defects. The length of a newborn's legs can be a sign there is a problem. Sometimes when a baby's legs are shorter or longer than they should be, it is a sign that they may have orthopaedic problems.

Healthy growth

During the first few months, a healthy newborn should gain about 142 g (5 oz) every week after losing some fluid weight in the initial days. They should also grow in height about 2.5 to 3.7 cm (1 to 1 1/2 inches) during the first month.

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About the Author

Jaclyn Castek is a freelance writer from Tampa, Fla. She has been a news writer for several newspapers and has written articles for a number of regional magazines. Castek received a Bachelor of Arts in journalism from the University of South Florida and is currently pursuing a master's degree in library and information science.