Normal Growth for Babies

From a paediatric's point of view, the growth of a child is extremely important. I mean, what's the point of treating a child who is not growing well? Conversely, a child who grows well rarely need treatment. Thus, knowing the normal growth pattern of a child is essential to avoid unnecessary worry or panic to both ourselves and the parents/

One of the parameters that will tell us whether the child is growing well recently is the weight. Whenever a paediatric patient have a problem, the first growth parameter that will be affected is the weight. Thus, it is essential we know the normal weight variation and gain among paeds patients. How do we know what weight is appropriate for the child?

The best way is of course by analysing the growth pattern using a growth chart. Growth chart can show us whether the child is failing to thrive, stunted, or just wasted with just one glance.

However, most of the time, especially in short case exams we do not have the luxury of a growth chart. Most of the time, someone will just ask us "Is the child's weight adequate?", and that can be the end of our exam.

There are some principles that need to be remembered. Firstly, when the baby was born, he will lose almost 10% of his birthweight during the 1st week. This is due to water loss, probably from inadequate milk production, or loss of amniotic fluid swallowed while in the womb. This loss of weight is absolutely physiological (provided the baby is active and feeding well), thus there should be no fuss about this. By the end of the second week, the baby should regain his birth weight.

From the 2nd week to 3 month of age, the baby should gain around 25 to 30 g per day depending on ethnicity and frequency of feeds. Thus, when a 2 month old baby with a birth weight of 3 kg come to us, the expected weight should range from 4.05kg to 4.3 kg.

From 3 month to 12 month of age, the expected weight of the baby can be calculated using the formula (X+9)/2, where X is the age of the baby in month. A shortcut method is that the baby's weight should double its weight by 6 month, triple its birth weight at 12 month

X=age in years from here onwards

From 1 year to 6 years of age, the weight can be calculated using the formula (2X)+8.
From 6 years to 12 years, the weight can be calculated using formula [(7X)-5]/2.

As for height, the child's height from age 2 to 12 years can be calculated using the formula 6X+77.

Of course, these are all estimations. It raises alarm that there may be something wrong with the growth of the child. Further investigations and reference to growth chart is needed to confirm the suspicion.

Head circumference is the last parameter to be affected by any malnutrition due to the brain sparing effect. However, head circumference measurement is essential in cases of developmental delay or cerebral palsy. Normal head growth will be 6cm in the first 3 month, 3cm in the next 3 month and 3 cm in the next 6 month giving a total of 12 cm in 1 year. After that, the head only grow around 2 cm per year. Note that in a premature baby, this rule only applies when his chronological age reach term. (e.g. a premature 34 weeker's head will only start growing as above when he's 6 week old.)