Promoting Healthy Growth

What Are The Stages of Child Growth & Development?

Parent’s worry. They always have. After all, our children are our future, and we want more than anything for them to grow up healthy and strong. But how do we know this fundamental, instinctual desire is being fulfilled? What is the norm for height and weight in a developing child? Through their early lives, from the prenatal period to infancy, to early and late childhood and into puberty, your child will grow by identifiable stages.

These stages of child growth and development are not necessarily hard and fast rules set that will apply to every child. Rather, they represent a sliding scale by which to judge the physical growth of your child within a set population, without really taking into account such mitigating factors as nutrition, environment, genetics, and hormones. Nevertheless, it is vastly important to see child growth and development stages as benchmarks by which to judge your child’s health. If they are not meeting the standards set by these stages then it may be a warning sign that their growth is in jeopardy and a consultation with a pediatrician may be advisable.

At the end of the day, your child is absolutely unique to the World—there has never been and never will be anyone like them. By paying attention to the following stages of child growth and development and being aware of the necessary nutritional, environmental, hormonal and genetic factors that play such a huge part in these stages, you can ensure that your child will grow up to be the healthy and happy examples of what they are: themselves.


The prenatal period represents the time from which the human zygote becomes an embryo, develops into a fetus and ends in childbirth. This gestation process usually lasts nine months and is conveniently separated by doctors into three trimesters in order to set goals and ensure maternal and fetal health. The first two trimesters represent the fetus’s most formative phases and are thus essential to healthy growth and development. During all three trimesters, every ounce of nutrition and oxygenated blood the fetus requires are delivered through the umbilical cord after having been filtered through the placenta.

This symbiosis between mother and fetus makes it essential that during the prenatal period the mother stays healthy and strong. More calories will need to be ingested in order to ensure the mother has some left over to spare for herself, while dangerous behaviors (such as smoking, drinking alcohol, consuming drugs, or participating in overly strenuous activities) should be avoided at all costs. However, though the trimester system is convenient to ensuring good health practices by the mother, it does not necessarily fully represent the growth and development of the fetus itself. There are, similarly, three stages of prenatal growth that follow closely, but not entirely, the trimester system.

Stage One: 4-20 Weeks

During the first stage of prenatal growth a healthy fetus will grow from a microscopic speck to over 25 centimeters (10 inches) in length. At this stage, responsibility rests entirely upon the mother to ensure nutritional health and solid growth, but even so, outside factors and interior complications can result in miscarriage.

Stage One is also the stage in which the most rapid development will occur in a child’s lifetime. Growing from a microorganism to nearly the size of a foot long ruler represents exponential growth in a relatively short time period. The proper weight by the end of this journey should be around 300 grams at 20 weeks and by the end your fetus should be looking like a rather large headed, skinny-bodied infant. Monitoring your fetus’s health and growth during Stage One will be essential to see it into the next stage of prenatal development.

Stage Two: 20-28 Weeks

This stage is identifiable by an increase in weight compared to length. A fetus’s body, prior to this stage often appears thin and bony, but once it has advanced beyond its twentieth week, the muscle will begin to form rapidly. From an average weight of 300 grams at its start, the fetus will be over a thousand grams by Stage Two’s end. Length will also increase to around 35-40 centimeters (14-16 inches) by the end of Stage Two.

This is due to a number of growth factors—hormones and proteins that stimulate cell production, healing, growth and specialization—that are present in all three stages of fetal growth and development. Fibroblast, Epidermal and Transforming growth factors play essential parts in transforming Stage One’s skeletal fetus into the healthy and plump infant that is the product at the end of Stage Three.  

Stage Three: 28-40 Weeks

The last Stage of the Prenatal Period will be a time of increased growth in weight and length(along with providing the finishing touches of the fetus’s mental and physical development). Between week 37 and 42 the fetus should be birthed (any time before or after this window is considered irregular, though you should consult your physician and family history for trends and outlying factors).

By the end of Stage Three (40 weeks) a healthy infant should be born to be around 50 centimeters (20 inches) in length and 3400 grams (around 7.5 pounds) in weight. Remember, these numbers can fluctuate due to sex, genetics and other such variables, but by the end of Stage 3 the result should be a healthy infant.


Of the stages of child growth and development, infancy (the first two years of a child’s life) can be the most stressful for the parent and most essential to the child’s future growth. Careful monitoring of your infant’s rate of development can help to allay the fear of hindrances to their healthy growth.

In the first few days of their life, an infant can lose up to 10% of its birth weight due to a number of causes. Unfamiliarity with the feeding process and loss of symbiosis with the mother are the usual culprits. The fact is, life outside the nutritional world of the placenta takes some getting used to, but your infant should re-gain most of its birth weight within two weeks. From then on there should be a steady increase in your baby’s weight (gaining 30 grams a day for the first 1-3 months is regular, dropping to 20 grams a day through months 3-6 and 10 grams through months 6-12).

By their fourth month out of the womb it is usual for an infant to be twice its birth weight (around 15 pounds), and three times its birth weight by the end of its first year (around 22-23 pounds). All these gains should be similar whether the infant is breast or formula fed, though a breastfed baby will usually see more rapid growth during the first 3 to 4 months of infancy before leveling out to formula fed numbers during the second year of life.

During this second year, the weight of your infant will not increase as dramatically as it did during the first. This is because the body has begun to establish a normalized growth pattern that will continue into childhood. By the end of their two-year infancy, a healthy child will usually weigh between 25 and 35 pounds depending on genetic and environmental factors.

As your baby is no longer in the nutritional cradle of its mother’s womb, growth in height will no longer be as dramatic as it was during those heady days. Throughout the first year of life an infant will begin to grow according to their genetic potential. However, since this period represents only the beginning phases of this switch from intrauterine growth, the end result after two years of infancy will usually look the same across the board—be it a boy or a girl, or whether or not the infant is genetically predisposed towards a certain height.

After the first year, an infant will have usually grown 25 centimeters (10 inches), while at the end of their second they should have grown a further 11-13 centimeters (about 4-5 inches). According to the U.S. Center for Disease Control, the average height of a two year old is 86 centimeters (34 inches) for girls and around 88 centimeters (34.5 inches) for boys. These averages fall on the 50th percentile line and do not necessarily suggest that your infant, be they smaller or larger by a few inches, are in any way on the wrong the side of what is considered normal. Height, especially, is a difficult to track and easy to fuss about quantity that will, as your infant progresses into childhood and adolescence, become ever more dependent on their genetic capability.


Childhood, the stage of child growth and development that is the most steady, is a period of small gains throughout many years. Boys and girls between the ages of two and nine will usually gain around 2 kilograms (about 4.5 pounds) per year until the onset of puberty. This steady rate of weight gain will often be in concert with an increase in height (a child will sometimes naturally put on excess weight before or during a growth spurt). Between the ages of 2 and 4, most children will add around 7.5 centimeters (3 inches) to their height, dropping off to 4-6 centimeters (1.5-2.5 inches) each year in their remaining years before puberty.

This height gain will be nonlinear as growth spurts last an average of 8 weeks and can occur seemingly at random over a given year. However, growth in height and weight should remain essentially congruous and steady over childhood. Genetics, diet, lifestyle, and nutrition will usually be the determining factor throughout this stage, and though we cannot do anything to change our genetics, ensuring a healthy and active lifestyle for your growing child will go a long way towards preparing them for the bodily changes and hormonal rigors of puberty.


Of all the child growth and development stages, puberty is probably the least entertaining for parents. It is, however, the last hurdle your child will have to overcome to achieve their adult height. Pubertal growth spurts will inevitably account for a fourth of a human being’s adult height and can be incredibly rapid. Girls tend to go through puberty before boys, usually during their ninth to eleventh years and can grow an average of 23-26 centimeters (9-10 inches) over a 24-36 month period.

For boys, who usually hit puberty around 11-14 years old, height gain will be between 26-28 centimeters (10-11 inches) on average over a similar period. These gains will, once again, be determined by the genetic capability of the individual and can fluctuate depending on a number of factors. By the time girls reach 15 years and boys reach 16-17, they will have reached their adult height (often called “bone age” as epiphyseal fusion occurs) and vertical growth will no longer be possible.

To enable this growth in height and to make way for the increase in bone density and muscle mass  that puberty often entails, weight gain is mandatory. Throughout the pubescent stage, boys will gain an average of 20 kilograms (44 pounds), while girls will gain 16 (35 pounds).

This can happen nearly all at once and before a growth spurt, leaving you and your puberty stricken teen concerned for their health. However, by the end of the puberty phase of child growth and development, a healthy and active teenager will achieve a weight congruent with their body type. Weight gain can fluctuate and take time, some may grow in height before they grow in weight, but by the end, given correct dietary habits and nutritional awareness, a happy medium should be achieved.

Each of these stages of child growth and development can be as exciting as they are anxiety inducing. The most important thing you can do as a parent or guardian is to monitor your child’s progress and keep your pediatrician updated. Always remember that your child is unique, and the road they travel to their final height and healthy weight will be one of a kind as well. 

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