Mid-Parental Target Height Calculation
For a 2-year-old girl with father's height 167 cm and mother's height 155 cm, the mid-parental target height is 154.5 cm using the standard Tanner formula. 1, 2
Calculation Method
Using the Tanner formula for girls:
- Formula: (Mother's height + Father's height - 13) ÷ 2 1, 2
- Calculation: (155 + 167 - 13) ÷ 2 = 154.5 cm
- Expected range: approximately 144.5-164.5 cm (±10 cm represents the 95% prediction interval) 3
Alternative Calculation: Molinari Formula
If accounting for secular trends (children being taller than parents by approximately 3.8 cm per generation): 1
- Formula for girls: (Mother's height + Father's height - 26) ÷ 2 1
- Calculation: (155 + 167 - 26) ÷ 2 = 148 cm
- This formula assumes generational height increases and may be less applicable if parents are already of current generation height 1
Clinical Application for This 2-Year-Old
The Tanner formula (154.5 cm target) is the recommended standard method and should be used as the primary reference point for monitoring this child's growth trajectory. 1, 2
Important Monitoring Considerations:
At age 2 years, this child may still be establishing her genetic growth curve. Healthy infants often cross centile lines in the first 3 years of life to establish a growth curve appropriate for their genetic potential. 1
Serial measurements over 4-6 months are more valuable than single measurements to assess whether growth velocity is appropriate (expected 4-7 cm/year during childhood after age 3). 1
Crossing several centile lines downward after age 3 years would suggest pathologic growth and warrant further evaluation. 1
Critical Caveats
These predictions assume both parents are healthy without chronic diseases affecting growth, and the child has no underlying medical conditions. 2, 4
When to Measure Parents Directly:
Always measure parental heights directly rather than relying on self-report. Fathers overestimate their height by an average of 1.7 cm, and 15% of fathers and 12% of mothers report heights inaccurate by more than 4 cm. 5
Partner-reported heights are even less accurate (fathers reported by mothers averaged 3.8 cm too tall). 5
Inaccurate parental heights lead to erroneous target height calculations in 30% of cases (deviation >2 cm from true target height). 5
When to Consider Further Evaluation:
If the child's actual height deviates significantly below the target height (154.5 cm) with abnormal growth velocity 2, 4
Bone age assessment via left wrist radiograph is the standard approach for assessing remaining growth potential and can improve prediction accuracy. 1, 2
Consider skeletal survey if height falls 3 standard deviations below mean and no other diagnosis is apparent. 1