How to correctly calculate body mass index for children?

The birth of a child is a great joy in the family. Pleasant chores of preparing for a new family member, changes in life, the first trip to the children's clinic. Every mother knows how much her baby weighed at birth.

All children are weighed from the first minutes of their life, and a visit to the pediatrician is not complete without this. This procedure is considered one of the most important during the examination. But not every mother can assess whether the child’s body weight is normal.

It is very important to monitor children's body mass index to prevent weight from getting out of control.

How to correctly calculate body mass index yourself?

In order to calculate correctly, it is necessary to find out such parameters of the child as height (in centimeters) and the exact value of body weight (in kilograms). No more devices are needed.

If you don’t have the Internet at hand, but you just need to find out your body mass index, then it’s very easy. In children, body mass index is usually calculated using the Keele formula. The baby's exact weight is divided by twice his height. The result will be a two-digit number.

Basic BMI indicators

After determining the child’s body mass index, it is necessary to compare the obtained figures and determine which parameters it falls into. The normal BMI value for children over one year of age ranges from 18.5 to 25.

• If the indicators are below the norm by more than 2.5 points, then this may indicate a significant lack of body weight in children. A body mass index below 16 suggests the possible presence of serious health problems, the development of anorexia.
• A value above the norm is also not a good result - it indicates the beginning of the development of obesity. A body mass index of up to 30 is a slight excess weight, which can be managed by introducing a diet and increasing physical activity. A body weight score of more than 30 confirms the development of obesity. These numbers should force parents to act as soon as possible. In this case, the help of a specialist is mandatory.

All this does not apply to babies from birth until they are one year old. Their norm values ​​are slightly different and range from 13 to 21.

Growth disorders

1. What is the normal growth rate for children?

The normal increase in height is 16-17 cm in the first 6 months of life and about 8 cm in the next 6 months. In the second year of life, growth increases by only 10 cm, in the third - about 8 cm and in the fourth year - 7 cm. Over the course of 5-10 years of life (before puberty), the increase averages 5-6 cm/year.

2. In what ways is height determined in children?

The first and most important method is to accurately measure body length. In children under 2 years of age, the best way to measure body length in a supine position is to place the child in a structure like a box with a retractable leg end. In children aged 2 years and older, height is measured standing, preferably using a stadiometer, which allows the measurer to lightly press on the child's chin while a movable bar touches the top of his head, and then interpret the measurement results. If this device is not available, the child should lean against the wall with his heels, buttocks, back and the back of his head. The bar is lowered at a right angle to the top point of the head, a mark is made and the result is measured. The use of scales with height marks is quite unreliable. You should also determine your weight and, if necessary, your head circumference.

The second way is the growth curve. It is clear that the more points that make up the curve, the better idea you can get about the child’s growth. A dot is just a dot, at least two of them are needed to draw a line! Finally, radiographs of bone growth plates provide important information about bone maturation and then objective maturation. For this purpose, in children over 2 years of age, radiographs of the left hand and wrist are taken and the epiphyseal ossification centers of the upper and lower extremities are calculated (bone age).

With accurate height and weight data, a carefully plotted growth curve, and bone age studies, you can quickly determine the cause of low height and schedule further testing.

3. Taking into account the growth curve, bone age and body length, how can familial (genetic) short stature be distinguished from other conditions?

Children with familial stunting grow at a normal rate, but they are below the optimal curve. In such children, the bone condition is approximately consistent with their age. For example, if the growth deviation of a 5-year-old child is more than 3%, but his growth curve is parallel to the lower limit of the normal curve, and the bone condition corresponds to 5 years of life, then, in all likelihood, we are talking about familial short stature. A simple formula helps determine how a child’s height is related to the height of his parents: you need to add the parents’ height in cm; add 13 if the child is a boy, or subtract 13 if the child is a girl; divide the total by two. The resulting height result of +_ 5 cm approximately corresponds to the expected height of an adult. If the expected height (on the continuation of the curve) approximately corresponds to that calculated by the formula, then there is a high probability that the child’s existing height is determined genetically. Conversely, if the predicted height is less than the calculated one, then other factors influence the shortening of the body. See examples 1 and 2 below.

4. What reasons other than genetics are most often responsible for short stature?

Constitutional growth retardation (constitutional short stature) occurs in 2% of children and is manifested by shortening of the body and delayed bone growth. These children typically experience a slowdown in growth between 18 and 30 months of age, after which growth occurs at a normal rate throughout the remaining years of childhood. At the same time, at all chronological age stages, bone growth is delayed. Continued growth retardation results in delayed puberty and physical development. Such children (usually boys) often have references to similar cases in their family history; There may also be a sharp slowdown in growth rate compared to normal pre-pubertal children. Growth, including teeth, skeleton, and pubertal development simply physiologically slow down. Completion of growth occurs at a later age, eventually reaching normal adult levels, taking into account genetic capabilities. See examples below.

5. How is constitutional growth retardation diagnosed?

The diagnosis of constitutional growth retardation is established based on the following characteristics.

1. Short stature.
2. The period of slow growth in the second year of life is replaced by a normal growth rate.
3. Slowing bone growth (bone age should be approximately equal to “age for height” - this point is in the middle of the perpendicular lowered from the growth point on the curve).
4. The presence of similar cases in the family history; delayed tooth growth; delayed puberty.

The diagnosis of constitutional growth retardation, based on the above criteria, does not require additional laboratory justification.

6. What is the effect of testosterone use in boys with constitutional growth retardation?

Short-term use of testosterone in constitutionally delayed boys accelerates growth and stimulates puberty without affecting final adult height or bone development. According to European scientists, the use of long-acting testosterone esters at 100-250 mg/month for 6 months, starting at bone age 12 1/2 years, has a positive psychosocial effect without negative somatic effects or a decrease in final adult height. Moreover, testosterone treatment improves the secretion of growth hormone, which also leads to a noticeable increase in growth. Clinically, boys experience pubertal changes, including enlargement of the genitals (but not growth of the testicles), growth of pubic and axillary hair, a deepening of the voice, an unpleasant odor of sweat, and acne. It is not surprising that significant personal changes also occur!

7. List the endocrine causes of short stature in children.

Non-endocrine causes account for 90% of cases among stunted children.

Among the most important endocrine causes, the following should be noted:

• growth hormone deficiency;
• excess glucocorticoids;
• congenital hypothyroidism;
• acquired hypothyroidism;
• pseudohypoparathyroidism;
• poorly controlled diabetes mellitus;
• rickets and other metabolic bone diseases.

8. Describe the etiology of growth hormone deficiency.

Idiopathic growth hormone deficiency occurs in only 1 in 10,000-15,000 children and is the most common etiological factor. In most cases it develops sporadically, but a number of hereditary cases have been described, sometimes with a specific deletion of the genes responsible for growth hormone. Other major causes of growth hormone deficiency are listed below.

1. Congenital Septoptic dysplasia Defects in the midline of the face or skull Congenital absence of the pituitary gland

2. Injuries Accidents, including birth injuries Consequences of violent acts against a child 3. Iatrogenic cases, after treatment with Operative Radiation Chemotherapy 4. Infections 5. Vascular diseases 6. Psychosocial disorders 7. Tumors of the hypothalamus and pituitary gland (craniopharyngioma, glioma, pinealoma , hamartoma, neurofibroma) 8. Histiocytosis 9. Resistance of target organs Laronoff type dwarfism Biological inactivity of growth hormone Nutritional disorders

9. How is growth hormone deficiency diagnosed?

If careful examination fails to detect other causes of growth failure, these children are tested for growth hormone deficiency. Since the secretion of growth hormone occurs intermittently, random research is pointless. Growth hormone should be determined after a series of physiological and pharmacological stimulating effects. Normal children usually respond to stimulation with an increase in growth hormone levels of 8-10 ng/ml, sometimes its level can increase to 30 ng/ml. For the results to be reliable, it is necessary to make sure that the child’s condition is euthyroid and that he does not have serious concomitant chronic diseases or psychosocial depression. Simultaneous testing of other pituitary functions includes determination of TSH and thyroid function, ACTH, cortisol and gonadotropins, since growth hormone deficiency may be associated with general hypofunction of the pituitary gland.

Drugs used in tests for the adequacy of growth hormone secretion

If pharmacological stimulation does not increase growth hormone levels above 8-10 ng/ml in all studies, then this is evidence of classic growth hormone deficiency.

Physiological stimulation includes sleep and physical exercise. In most healthy children, growth hormone is secreted briefly after sleep and for 20 to 40 minutes after 20 minutes of vigorous exercise. These tests are only useful for screening.

More often, pharmacological stimulation is used to diagnose growth hormone deficiency. Various drugs can be used. It is necessary to do at least two tests, since on this day the patient may react to more than one agent. All tests require overnight fasting.

10. What role does the determination of somatomedin-C (insulin-like growth factor 1) play in diagnosing growth hormone deficiency?

Somatomedin-C [insulin-like growth factor-1 (IGF-1)] is a special class of serum peptides that interact with growth hormone. IGF-1 is currently being actively studied and is recognized to play a critical role in growth. In the diagnosis of growth hormone deficiency, the study of somatomedin-C is presumptive, but not definitive confirmation. In general, the concentration of somatomedin-C decreases with hypopituitarism and increases with acromegaly. A normal somatomedin-C level generally indicates intact growth hormone production and can be used for screening, but does not replace post-stimulation growth hormone testing for definitive diagnosis. Low somatomedin levels - May indicate growth hormone deficiency, but it is sometimes associated with starvation, chronic illness and hypothyroidism. ! The fact that somatomedin-C levels do not change throughout the day, unlike growth hormone levels, makes the determination of IGF-1 very attractive. However, the level of this hormone varies with age (very low up to 6 years), and this determines the above-mentioned limited use in clinical practice.

Normal content of somatomedin-C

Source: Nichols Institute, San Juan Capistrano, S.A.

11. How is idiopathic growth hormone deficiency treated?

Over the past 30 years, children with classic growth hormone deficiency have been treated with great success. Currently, growth hormone is produced using recombinant DNA technology rather than being extracted from the human pituitary gland. Many questions remain regarding dosing, but in most cases children are prescribed 6-7 injections per week for a total dose of approximately 0.30 mg/kg/week. Injections are given subcutaneously. Since the effect of growth hormone wanes after several years of therapy, accelerated growth (rate > 10-12 cm/year) is usually observed in the first and second years of treatment, and then it decreases to normal or one and a half times higher during subsequent years of treatment. During the entire period of treatment, it is necessary to carefully monitor the content of thyroid-stimulating and other pituitary hormones. Bone x-rays are repeated annually to evaluate ongoing growth and the expected time of onset of puberty.

12. How is the final length predicted for children treated for idiopathic growth hormone deficiency?

Treatment with growth hormone simultaneously promotes elongation and proportional maturation of bones. Although most patients' growth curve approaches normal after initiation of treatment, and adult height is much higher than predicted before initiation of therapy, in many patients the final results still do not reach genetically possible values. Previously, researchers noted that after treatment of children, the final body length of an adult is 2 standard deviations lower than that calculated from the half-sum of the parents' height, while without treatment, the adult's height differs from the genetically determined one by 6 standard deviations. It is likely that these treatment results could be improved by using higher doses at shorter intervals. In addition, if the diagnosis is made at an early age and treatment is started immediately, the prognosis for final growth is much better than if treatment is started late. The more pronounced skeletal maturation at the time of diagnosis, the worse the final outcome of treatment. Children with idiopathic growth hormone deficiency respond better to treatment.

13. When should growth hormone treatment be stopped?

In children with idiopathic growth hormone deficiency, discontinuation of therapy is determined by the degree of maturation of bone structures, and not by the patient's age or duration of treatment. Treatment is often stopped when bone maturity reaches 15 (96% height) to 16 years (98% height) in boys and 14 years (98% height) in girls.

14. Which syndrome is most often treated with human growth hormone?

Turner syndrome (45 XO or mosaic variants) in girls is more often associated with short stature, which, apparently, is not caused by insufficient estrogen production. Currently, it is customary to treat sick girls with growth hormone or its combination with estrogens or oxandrolone.

15. What is the prognosis for girls with Turner syndrome who receive growth hormone medications?

The use of growth hormone for the treatment of Turner syndrome has been extensively studied for over 6 years. Girls treated during this period were 14 cm longer than expected adult height. In the group of women who completed treatment, the average height above expected length was 8.8 cm. It is clear that growth hormone increases actual body length , increasing the rate of growth, but not accelerating bone maturation. This therapeutic approach can be extended by additional administration of low doses of estradiol or oxandrolone. The result of treatment may be not only an improvement in growth rates in adults, but also a normalization of growth rate in childhood.

16. What other syndromes may present with short stature and require the use of growth hormone?

Since human growth hormone is readily available, its use in several syndromes associated with short stature is being investigated. The bulk of such patients are children with Noonan syndrome, Russel-la-Silver dwarfism, Prader-Willi syndrome and Down syndrome. In addition, hundreds of children with kidney failure and after transplantation receive similar treatment.

17. What are the possible risks of using growth hormone drugs?

Glucose intolerance or hyperglycemia has been described during growth hormone therapy; but in reality, no adverse effects occurred with standard doses (up to 0.35 mg/kg/week). In 1982, several patients treated with pituitary-derived growth hormone died from Jakob-Creutzfeld disease, a degenerative disease of the nervous system caused by prions with a long latent period. It turned out that the pituitary gland extract was contaminated with previral particles. As a result, the use of pituitary-derived growth hormone was discontinued; Since 1983, only growth hormone obtained using DNA recombination technology has been used in the USA.

Recently, the question of the relationship between growth hormone and leukemia was raised. Worldwide, approximately 35 patients treated with growth hormone developed leukemia. None of the affected children in North America were treated for idiopathic growth hormone deficiency. On the contrary, the risk appears to be related to the presence of pre-existing diseases in children or previous chemotherapy and radiotherapy. Overall, the risk of leukemia in North America (based on a small number of observations) has increased fourfold.

Finally, approximately 25 children treated with growth hormone developed pseudotumor cerebri. The vast majority of them were treated for short stature associated with severe kidney disease or previous transplantation.

18. Should growth hormone be prescribed to short children without growth hormone deficiency?

Currently, this issue is the subject of fierce debate among pediatric endocrinologists. Of course, such children make up the majority among the huge number of stunted children. Several short-term observations of small groups of patients have demonstrated a sustained increase in growth rate after the use of growth hormone in children who did not have endocrine pathology. There was no disproportionality in bone development. In this case, the response in the form of accelerated growth was also greatest in the first year of treatment and decreased in the second year. Since no work has been able to trace the final body length of an adult, the question remains unclear: how does treatment with growth hormone affect the body length of an adult? On the one hand, some children with normal levels of growth hormone may grow at a slow rate and do not reach the adult body length calculated based on the anthropometric data of the parents. Such children may produce biologically inactive hormones or have inadequate daily production. At the same time, there is no clear evidence that growth hormone can increase adult height, but it is unlikely that suffering children should wait until the research results are completed, since the treatment may significantly benefit them.

On the other hand, a huge number of short children grow at a normal rate. Growth hormone increases short-term growth rate in many children, but there is no evidence of the effect of treatment on adult length. Expensiveness, potential risks, and uncertain success make this treatment problematic.

19. How does the growth process in children with excess glucocorticoids differ from that in children with exogenous obesity?

Excess of steroids, both iatrogenic (more often) and endogenous (less often), leads to disruption of the process of linear growth. The mechanism is based on direct metabolic disruption, including increased protein catabolism for energy, decreased lipolysis, and decreased collagen synthesis. Glucocorticoids also have an inhibitory effect on growth hormone production, increasing somatostatin levels and suppressing the intermittent release of growth hormone. In addition, they suppress the production of IGF-1. The result of all these processes is that most children with excess steroids are short in stature. In typical cases, their weight-to-length ratio is increased and obesity develops. Unlike adult patients with Cushing's syndrome,

children obesity usually develops proportionally; In addition, an important distinguishing feature of this disease is muscle weakness.

In turn, children with exogenous obesity often experience accelerated linear growth, so that they look not only plump, but also quite tall for their age.

20. What conditions are accompanied by accelerated growth in childhood?

In contrast to the large number of diseases in which growth is slowed or suppressed, there are relatively few conditions that result in accelerated growth. Most often, with the exception of genetically tall people, such conditions are cases of constitutional accelerated growth. As would be expected, these children experience accelerated bone maturation, accelerated growth, and early puberty.

Excess growth hormone is rare in children, but it results in increased body length rather than excess bone growth because the growth plates are open. Increased production of growth hormone is characterized by an increase in the content of growth hormone and extremely high levels of somatomedin-C. Syndromes accompanied by an increase in body size and rapid growth are listed below.

1. Genetically determined.
2. Constitutionally accelerated growth.
3. Klinefelter syndrome (47 XXY) - tall height, small testicles, late puberty.
4. Pathology of connective tissue: Marfan syndrome - high growth, arachnodactyly, excessive mobility in the joints, ectopia of the Stickler lens.
5. Excess growth hormone (pituitary gigantism).
6. Soto syndrome (cerebral gigantism) - macrocephaly, progressive gigantism, dilation of the ventricles of the heart, mental retardation, accelerated bone maturation.
7. Hyperthyroidism.
8. Excess androgens: early puberty; congenital adrenal hyperplasia; androgen-producing tumor.
9. Excess estrogen: early puberty; congenital adrenal hyperplasia; estrogen-producing tumor.
10. Obesity.
11. Beckwith-Wiedemann syndrome - macroglossia, umbilical hernia, hypoglycemia, macrosomia in newborns.
12. Homocystinuria - arachnodactyly, mental retardation, homocystin in the urine.

21. What is done with adolescents treated with growth hormone who entered puberty too early?

Some children, especially those with a history of head radiation, develop growth hormone deficiency and precocious puberty. The time period between thelarche and menarche in girls is shortened. Unfortunately, in irradiated children, premature development may be followed by a deficiency of gonadotropins. In fact, precocious development, by promoting accelerated growth, may mask growth hormone deficiency. Recently, these children have been receiving combination therapy with growth hormone and a gonadotropin-releasing hormone (GnRH) analogue to suppress puberty and close the epiphyses before the child reaches a certain height. This therapy allows one to achieve normal growth into adulthood.

The easiest way to calculate

The easiest way to find out your child's body mass index is through the Internet. It will take just minutes and will give the most reliable results.

The online calculator takes into account the gender, height, weight and age of children. The result should be a two-digit number, which is the body mass index.

A special program will not only calculate BMI itself and show acceptable limits, but will also identify the presence of a problem situation or its absence.

It must be remembered that all children are different and in certain children, a body mass index exceeding the normal limits does not always signal a disease. About 10% of children will never meet the set limits, which is considered their individual norm. Remember that only a doctor can determine this.

What is the weight:

In accordance with age standards and calculated body mass index, children are divided into categories:

• Severely underweight. Dangerous for children. It is characterized by extreme exhaustion, which is visible to the naked eye. The condition is characterized as critical. Consultation with a specialist and a rehabilitation plan are necessary immediately.
• Underweight, low weight. First of all, it involves going to a children's clinic and reviewing feeding. The child may be pale, passive, and slow to respond to external stimuli.
• Less than average. This characteristic may not cause suspicion; the body mass index is slightly lower than usual, which is considered acceptable. Don't think there's nothing to worry about. Further changes in parameters should be monitored and their decrease should not be allowed.
• Average weight. Corresponds to the normal development of children. Health does not cause any concerns. Such data are optimal for further growth and physical development.
• More than average. The beginning of gaining excess. In the future, weight gain is possible, which will lead to deterioration of health. Probable first degree of obesity. It is necessary to take measures not to increase the data, adjust the diet and increase the child’s physical activity.
• Very big. Signals the presence of obesity of the first, second and third degrees. Nutrition correction is carried out by a specialist after a certain examination.
• Weight does not correspond to age. Such conclusions can appear in case of serious developmental pathologies that affect the height and weight of the baby. Also, such numbers may indicate that you entered the data incorrectly when calculating your BMI. If all the indicators are correct, then the child needs the help of a doctor.

Height-to-weight ratio in children under one year of age

Young parents should know that in the first few days after birth, children lose about 8% of their original weight. This is fine. As a rule, 7-10 days after weight loss, the child recovers and gets better again. The first year of life is a period of constant changes in height and weight, they occur monthly. Thanks to this, doctors can understand whether the baby is developing and eating properly.

On average, in the first 6 months, babies gain about 700, sometimes 750 grams every month. Starting from the 7th month, the rate decreases, and over the next six months, children gain 350-500 grams every month. This is explained by this motor activity, which begins to noticeably manifest itself just after six months of life. If we consider a year of life in general, then by the end of it children weigh three times more than at birth. As a rule, the weight is from 8 to 12 kg. Growth is increasing no less rapidly. By the first birthday it increases by approximately 25 cm - to 70-79 cm.

Correspondence of height and weight for a girl under 1 year old

Correspondence of height and weight for a boy under 1 year old

The rate of height and weight gain depends on many factors. Sometimes indicators grow uncertainly. This can be explained by the following reasons:

• Transmission of infectious diseases.
• Prolonged diarrhea.
• Allergies of various types.

Lack of normal nutrition (artificial feeding, like mixed feeding, does not contribute to completely healthy development processes).

Only a pediatrician can determine the exact cause of the problem after diagnosis. Based on the conclusions drawn, he will also give recommendations on nutrition and other nuances.

What to do if you are overweight or underweight?

Weight problems should never be ignored. Osteoporosis, anemia, weakened immunity, disorders in the endocrine system - this is a small part of what threatens a child with a large deviation in weight.

When malnourished, children may experience dysfunction of vital organs, hair loss, general apathy and fatigue. With obesity, the spine is the first to suffer and the risk of heart disease increases. If measures are not taken in time, the consequences may be irreversible.

Measures to take:

• First, you need to determine the reason for the weight deviation in one direction or another. If you don’t know the origins, then it will be impossible to prescribe the correct correction and treatment.
• Determining the beginning of the problem. Whether the child was born with a deficiency or excess weight, how he gained weight in the future.
• Analyze the child’s nutrition, whether it corresponds to a healthy lifestyle, and whether it is suitable for a given age.
• A visit to a doctor - pediatrician, endocrinologist, gastroenterologist, pediatric nutritionist. A competent specialist will definitely conduct a differential diagnosis to find out whether underweight or excess body weight is an individual feature. An attentive doctor will collect a complete history of past or congenital diseases, dietary habits, living conditions, the baby’s activity, attitude towards food (spitting up, refusing food, constant feeling of hunger, chronic overeating, selectivity in dishes, eats only certain foods).
• Collection of analyses. The main ones that may be needed are blood, urine and feces sampling.
• Prescription of treatment when a specific disease or pathology is identified.
• Prescribing a diet, organizing proper balanced nutrition. The amount of proteins, carbohydrates and fats in dishes must be observed exactly as prescribed. It is possible to take microelements and children's vitamins if they are deficient in the body.
• Organizing a proper daily routine - daily walks in the fresh air, doing gymnastics, exercise therapy, timely sleep during the day and evening, meal schedules.

Parents should not forget that their own lifestyle directly affects their children. Social factors such as lack of mobility, overeating, excess fatty and high-calorie foods in the diet of adults are copied first.

About BMI centile tables

Children and adolescents grow every day. Of course, they all develop differently, but increases also have their own established measures. For a more accurate assessment of full development in pediatrics, centile tables are used.

Parents can use them themselves so as not to miss the development of pathology in the baby from birth. These tables estimate the ratio of height and body weight and indicate the norms of physical development of children.

All you need is a scale and a measuring ruler. For children under two years of age, you should find special scales to ensure accurate data. If there are none, then you can first weigh the adult, then pick up the child and repeat the procedure.

Table of average anthropometric data of children in the first year of life