> Introduction to Child Ailments & Diseases

An infant becomes a child at around the age of twelve months when he or she begins to talk, and also tries to stand up for the first time. At this age most children weigh about three times their birth weight. A year later they weigh about four times birth weight. After that weight gain and height gain slow down to around 2.3-3.0 kg (5-6 lb) and 5cm (2 in) per year; at puberty physical development speeds up again. Smaller than average children may have smaller than average parents - growth is partly governed by genetics - but nutritional or hormonal deficiencies can also lead to smallness.

Congenital illnesses which affect the heart, lungs, and digestive system can also hinder growth. Emotional deprivation can hinder it too. Abnormal tallness is more unusual, and in most instances is due to over-secretion of growth hormone, a tendency which may be inherited. Childhood ends at puberty, which occurs a little later in boys than in girls; for most girls puberty begins between the age of 11 and 13, but for most boys it arrives six months to a year later.

Until about the age of seven the fastest growing system in a child's body is the lymphatic system, a sophisticated chain of defences against infection. Swollen lymph glands, especially in the neck, are a sign that the system is being tested and that invading bacteria and viruses are being identified and destroyed. Most adults are not vulnerable to the germs which cause the diseases we think of as 'childhood diseases' precisely because they fight and conquer them in childhood, when their lymphatic system is at its most active. Many childhood diseases - mumps, measles, rubella, whooping cough - are more serious in adults than in children.

Development of the nervous system depends partly on a process called myelinization. Myelin is a fatty substance which forms a sheath around certain nerve fibres, and speeds up the rate at which electrical impulses travel along them. Those parts of the brain responsible for planning and thinking ahead myelinize between the age of six and ten. Some nerve tracts, those concerned with fine control of movement, for example, do not fully myelinize until the age of four.

A three-year old throwing a ball clearly has more control of their shoulder and arm than of their wrist and fingers. Catching a ball is a different matter; it requires split-second timing and coordination. Throw a ball to a two-year old, and they will look at you, not at the ball; they will make no movement to catch it. Their brain and nervous system cannot process information about distance, speed, and body movements in space quickly enough to enable them to make an attempt at catching. But by the age of five most of their catching attempts will be successful, if a little jerky; if they drop or miss the ball sometimes it is probably because they are trying to keep their eye on three things at once, on the ball, on their hands, and on the thrower!

Children's paintings and drawings are also pointers to mental development. Most one- and two-year-olds enjoy making their mark on the world with pencils and coloured crayons. Slowly the scribbles take on a more deliberate, intentional character; though still unrecog¬nizable, they are clearly symbolic of something. By the age of three the squiggles turn into faces; by the age of six or seven the faces acquire bodies and limbs, even if the proportions are a little odd; by the age of eight or ten there are attempts at pattern and perspective.

There are many ways of assessing whether a child is developing normally. Comparing your child's height and weight with those of children of a similar age is one way; comparing the ages at which he or she acquires certain skills is another. But it must be stressed that there is a great deal of variation in the ages at which children reach a certain height or weight or level of performance. What is more important is the overall pattern or sequence of events. A child may be consistently under average height and weight for his or her age, but nevertheless gain a consistent number of inches and pounds in the years between infancy and puberty. What is important is sustained growth throughout childhood, with no plateaux or troughs.

With mental and physical skills too it is a normal sequence one is looking for as much as precocity or delay. Certainly the majority of children have begun to say Mama and Dada by the age of twelve months, but some children say their first words as early as nine months or as late as fifteen. Most children can do up buttons by the age of four, but some can't; they may still be mastering the knack of putting arms through sleeves. With this caveat in mind, here are some of the milestones which most children can be expected to reach between the age of one and five. A delay of a few months is not significant; longer delays may be significant if growth and general health are poor.

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