What is the predicted adult height of a child if the father is 186cm tall and the mother is 157cm tall?

Predicted Adult Height Based on Parental Heights

For a boy, the predicted adult height is approximately 178 cm (range 168-188 cm), and for a girl, approximately 165 cm (range 155-175 cm), using the genetic target height calculation based on mid-parental height. 1

Calculation Methods

Standard Tanner Formula (Most Widely Used)

The genetic target height calculation uses the following formulas 1:

For boys:

• (Mother's height + Father's height + 13) ÷ 2
• (157 + 186 + 13) ÷ 2 = 178 cm
• 95% confidence interval: ±10 cm (168-188 cm) 2

For girls:

• (Mother's height + Father's height - 13) ÷ 2
• (157 + 186 - 13) ÷ 2 = 165 cm
• 95% confidence interval: ±10 cm (155-175 cm) 2

Alternative Molinari Formula (Accounts for Secular Trends)

This formula assumes a generational height increase of 3.8 cm 1:

For boys:

• (157 + 186 + 10) ÷ 2 = 176.5 cm

For girls:

• (157 + 186 - 26) ÷ 2 = 158.5 cm

Important Clinical Considerations

Heritability and Accuracy

• Height is 74-80% heritable, meaning parental heights explain approximately 36-40% of the variance in children's final heights 2, 3
• The standard mid-parental height method has a prediction error of approximately ±10 cm (95% confidence interval), which is substantial 2
• Recent data shows children are on average 2.7 cm taller than predicted by traditional target heights, reflecting ongoing secular trends 3

Population-Specific Variations

• The Tanner formula was developed from predominantly white European populations and may require adjustment for other ethnic groups 4
• For Taiwanese populations, different coefficients are used: boy height = 79.3 + 0.56 (midparental height); girl height = 35.2 + 0.76 (midparental height) 4
• Generational height increases vary by population, ranging from 0.7-1.0 cm in Sweden to 4.2-4.8 cm in Hong Kong Chinese 4

Key Caveats and Pitfalls

The prediction assumes:

• Both parents are healthy without chronic diseases affecting growth 1
• The child has no underlying medical conditions (chronic kidney disease, endocrine disorders, malnutrition) 1
• Normal nutrition and metabolic status throughout childhood 1

Common errors to avoid:

• The Tanner method may underestimate target height by up to 6 cm for children with very short parents (mid-parental height <163 cm) 2
• Different prediction algorithms show substantial disagreement, with kappa values as low as 0.21, particularly problematic when making treatment decisions 5
• Single measurements are less valuable than serial growth measurements plotted over time to assess growth velocity 6, 7, 8

When to Investigate Further

Consider evaluation for growth disorders if the child's actual height deviates significantly from predicted target height, particularly if:

• Growth velocity is abnormal for age 1
• Height falls more than 2 standard deviations below target height 2
• Bone age assessment shows significant advancement or delay 1