Average Baby Weight: What are the Norms? Overweight and Underweight

No matter what the average baby weight norm is, babies hardly check with them: some babies are born big, others – very small, and the third falls exactly “in the middle” section. What does it depend on? In what cases is the weight of a newborn important? And is it possible to “correct” the weight of the baby during pregnancy? Let’s find out.


Norms of Weight in Newborns

Standard indicators of birth weight are 2.8 kg – 4 kg with height – from 46 to 55 centimeters. Experts note that today, more and more big children are being born – the “heroic” weight of a newborn around 5 kilograms has ceased to be so rare.

According to World Health Organization, the weight of children at birth can be classified as follows:

Girls weight

ScoreVery lowLowBelow averageAverageAbove averageHeavyVery heavy
Weight (kg)

Boys weight

ScoreVery lowLowBelow averageAverageAbove averageHeavyVery heavy
Weight (kg)

According to these tables, indicators that fit into the frames from “below average” to “above average” can be assessed as a norm. Indicators “low” and “very low”, “heavy” and “very heavy” are a reason for more attention of specialists.

Keep in mind that weight itself is not as important as its compliance with the period of gestation. For example, a child born at week 40 with a weight of 2 kg and a child at 32 weeks with the same weight is two completely different children.

The main role is not played by the weight parameters themselves or their correspondence to the average indicators, but by the ratio of both height and weight of the baby. This value allows you to determine the Quetelet index – weight in grams, divided by height in centimeters. If the value is in the range of 60 to 70, this is considered normal for full-term babies.

Also, keep in mind that all the above data and standards are valid only for babies born on time. For premature babies, there are other criteria.

Comment of an Expert

There are special tables of the average baby weight and height of the child to the period of gestation – for boys and girls, respectively. Of course, the use of these tables can only give an approximate picture, since each country and each region may have its characteristics. Correct data for such tables is a serious problem, but World Health Organization (WHO) is already working on this. Regarding the tables that are used now – some examples can be given, even for full-term newborns.

The “correct” weight can be different: for example, with a gestational age of 37 weeks (this is a full-term baby), a weight of 2,850 g can be considered “correct”, while for a child with a gestational age of 41 weeks this weight will be considered insufficient. On average, the weight of a full-term baby from 3 to 4 kg can be considered sufficient.

The Weight of the Newborn and the Physique of the Parents

It is believed that big parents often give birth to big children and slender and short women bear miniature babies with low weight. It is also noted that parents who themselves were born large, are more likely to have a child weighing 4 kg or more.

Doctors say that the weight of the fetus and the newborn child doesn’t depend much on the parent’s physique. In the womb, all babies develop according to the same laws.


Comment of a Specialist

You can relate the weight of the newborn with the weight and height of the parents, but to a greater extent, this manifests itself later when the baby grows up. A graceful woman 150 cm tall is not supposed to give birth to a 2 kg full-term baby. And a tall woman with a weight closer to 90 kg is not supposed to deliver a five-kilogram baby, not at all!

Approximately the same indicators are relevant for them, although the compilation of special tables and programs determining the relationship between the weight and height of the child with the parental parameters is also under development.

Weight “By Ultrasound” and Weight at Birth

Sometimes, future mothers begin to worry about the weight of the baby long before the birth. During an ultrasound, the doctor who carries out the screening always calculates the estimated weight of the fetus based on the data on gestational age, head and tummy circumferences, femur length, and biparietal size of the fetal head (distance between the outer and inner contours of both parietal bones).

If the estimated weight of the baby differs from the accepted norms upwards or downwards, but at the same time there are no deviations in the state of the placenta and fetus – this is not a reason for worries.

Comment of an Expert

It is impossible to precisely weigh the fetus based on ultrasound. What’s more, the estimated weight of the baby very rarely coincides with the actual weight of the newborn.

Average Baby Weight During Pregnancy

In some cases, the small size and weight of the fetus may indicate the lag in the development and the presence of pathologies of pregnancy. A serious discrepancy between the physical development of the fetus and the term of gestation is called fetal hypotrophy or intrauterine growth retardation syndrome.

There are 2 forms of Malnutrition:

  1. Symmetric form of hypotrophy. It is noted already in the early stages of pregnancy, when all the parameters of the fetus, measured by ultrasound is less than the norm.
  2. Asymmetric form of malnutrition. It develops after 28 weeks of pregnancy. It is characterized by uneven development of the fetus. On ultrasound, the doctor can determine if the size of the head and body of the fetus does not match the abdominal circumference.

Such intrauterine growth retardation begins if the fetus receives insufficient nutrition. As a rule, it is associated with pathologies of the placenta.

The Reasons for this may be:

  • Malnutrition
  • Bad habits
  • Chronic maternal diseases
  • Genetic pathology
  • Infections

In other cases, the ultrasound doctor, on the contrary, notes the size of the fetus is too large compared to the norms.

What to do if during the ultrasound study the weight doesn’t correspond to the norm? Is it possible to somehow affect the weight of a baby who has not yet been born?

Comment of a Specialist

“Weight correction” by changing the lifestyle of a pregnant woman with a fetal weight deficit is impossible since the developmental delay is most often associated with the pathology of the placenta (chronic fetoplacental insufficiency), which does not fulfill its functions of nutrient delivery to the fetus. Sometimes the cause may be the child’s diseases, including genetic pathology.

A large weight of the fetus also cannot be corrected, because the child cannot lose weight in the womb. In any case, a woman’s nutrition should be complete and balanced and contain not only all the necessary nutrients in the required amount (proteins – of animal and vegetable origin, carbohydrates and fats) but also trace elements and vitamins. Following a strict diet so that the baby is “small” or does not “continue to grow further” in the last weeks of pregnancy is not an option, because it can do more harm than good, including premature birth.

Overweight Newborn

Most often, large babies whose weight is beyond the average baby weight (according to the WHO table) are completely healthy. But in some cases, being overweight in a newborn is a symptom of disorders that require attention and control by a physician.

Special attention is required when:

  • The mother had diabetes or other endocrine disorders during pregnancy
  • The baby has signs of postmaturity (no original lubricant on the baby’s body, dryness and maceration (stratification, peeling) of the skin)

Expert’s Comment

Babies born overweight can be “constitutionally large” and healthy at the same time. But there are also children whose overweight may be associated with metabolic disorders in the mother during pregnancy. In the first days after birth, such children often have health problems, in particular, a tendency to low blood glucose levels, respiratory disorders, etc.

Lack of Body Weight of the Newborn

Full-term babies with a deficiency of body weight (hypotrophy) need special attention and care in the first months after birth.

For the treatment of malnutrition, babies and their mothers are prescribed a special diet, strictly individual for each case. This is because, on the one hand, a newborn with low body mass needs an increased amount of nutrients, and on the other hand, nutrition that is as gentle as possible for the gastrointestinal tract.

A Specialist’s Comment

The birth of an underweight child is a serious problem, even more, serious than the birth of a large child. The lack of mass occurs when the child in utero loses the necessary substances. Accordingly, the development of all organs and tissues occurs in adverse conditions, which is accompanied by dystrophic changes and impaired functions of organs, the more pronounced they are – the greater is the weight deficit. Therefore, the problem should be considered broader than just “weight gain”.

Small children are more prone to metabolic disorders, and at an older age are more likely to be overweight, and in adulthood, obesity and the associated hypertension and type II diabetes mellitus are also possible. This does not mean that it is necessary to “limit the child’s nutrition”. it is just necessary to remember that nutrition must be balanced and of high quality, containing all the necessary nutrients, vitamins, and microelements.