Calculadora de Predição de Altura Infantil

Predicting adult height from parental height works because height is strongly heritable, with twin and family studies attributing roughly 80 percent of the variation between people to genetics. The mid-parental method is the standard clinical starting point, and its usefulness lies less in the predicted number than in the range around it, which is wide enough to make the prediction a screening tool rather than a forecast.

A fórmula

Boys:  ((mother height + father height) / 2) + 6.5 cm
Girls: ((mother height + father height) / 2) - 6.5 cm
Target range = prediction plus or minus about 8.5 cm

• Both parent heights measured, not reported, wherever possible
• The 6.5 cm adjustment reflects the average adult height difference between men and women

Mid-parental height method as used in paediatric growth assessment, following the approach described by Tanner and colleagues.

What the prediction is for

In clinical practice, mid-parental height is used to judge whether a child current growth curve is consistent with their genetic potential, not to tell parents how tall a child will be. A child tracking on the 10th centile whose mid-parental target also falls near the 10th centile is growing exactly as expected. The same child with a mid-parental target on the 75th centile is the one who warrants investigation.

This is why the range matters more than the point estimate. About 95 percent of children fall within roughly 8.5 cm either side of the mid-parental prediction, which is a spread of 17 cm. A prediction of 175 cm therefore means, honestly stated, somewhere between about 166 and 184 cm.

• The method assumes both biological parents reached their own genetic potential. Childhood illness or undernutrition in a parent makes the target an underestimate.
• Parent heights should be measured where possible. Self-reported heights are systematically overstated, and both parents overstating shifts the prediction upward.

Growth patterns through childhood

Growth is not steady. Roughly half of adult height is reached by about age two, growth then settles to a fairly constant rate through mid-childhood, and the pubertal growth spurt adds a final burst that differs in timing and magnitude between individuals. Because timing varies, two children of the same age and height can end up substantially different in adult height.

• Girls typically finish growing around 14 to 16, boys around 16 to 18, when the growth plates fuse.
• A bone age X-ray of the hand and wrist gives a much better individual prediction than any parental formula, because it shows how much growth potential remains.

When short stature is worth investigating

Most short children are healthy children of short parents, or children with constitutional delay who will grow later. The features that prompt assessment are not shortness itself but the pattern around it.

• Height well below the mid-parental target range rather than simply on a low centile.
• Crossing downward through centiles after age two, when a child should be tracking.
• A growth rate below about 5 cm per year in mid-childhood.
• Disproportion between limb and trunk length, which points to a skeletal dysplasia rather than to a growth hormone or nutritional cause.
• Short stature with other features: chronic symptoms, delayed puberty, or unexplained weight loss.

Limitações

• The prediction interval is wide, roughly 17 cm across for 95 percent of children, which makes it a screening tool rather than a forecast.
• It assumes both parents achieved their own genetic potential, which is not true where a parent had significant childhood illness or undernutrition.
• Self-reported parental heights are systematically overstated and shift the prediction upward.
• The method does not apply to children with conditions affecting growth, including Turner syndrome, skeletal dysplasias, growth hormone deficiency and chronic disease, for which condition-specific charts exist.
• Bone age assessment gives a substantially better individual prediction, and is what clinicians use when the question actually matters.
• A prediction cannot diagnose anything. Concerns about growth should go to a clinician who can assess the full picture.

Perguntas frequentes

How do you predict a child adult height?

The mid-parental method: average the two parents heights, then add 6.5 cm for a boy or subtract 6.5 cm for a girl. About 95 percent of children end up within roughly 8.5 cm either side of that figure.

How accurate is the mid-parental prediction?

Only moderately. The 95 percent range spans about 17 cm, so a prediction of 175 cm honestly means somewhere between about 166 and 184 cm. It is used clinically to check whether a child growth is consistent with their family, not to forecast a number.

At what age do children stop growing?

Girls typically finish around 14 to 16 and boys around 16 to 18, when the growth plates fuse. Timing varies considerably, and later puberty generally means a longer growth period.

My child is short. Should I be concerned?

Most short children are healthy children of short parents or have constitutional delay. What warrants assessment is height well below the mid-parental target, crossing downward through centiles after age two, a growth rate under about 5 cm a year, or disproportion between limbs and trunk.

Is there a more accurate way to predict height?

Yes. A bone age X-ray of the hand and wrist shows how much growth potential remains and gives a considerably better individual prediction than any parental formula. It is what clinicians use when the answer matters.

Referências

1. MedlinePlus. Normal growth and development.
2. World Health Organization. Child Growth Standards.
3. MedlinePlus. Growth disorders.
4. MedlinePlus. Bone x-ray.