Guide
Bayley-Pinneau vs mid-parental height
Two different questions about a child's adult height: what the skeleton says today, and what the parents' heights suggest. When clinicians use each.
Two questions, two methods
Mid-parental target height asks a genetic question: given these parents, where would we expect this child to land? It uses only parental heights and sex, no measurement of the child at all.
Bayley-Pinneau asks a maturation question: given where this child's skeleton is today, how much growth is left? It uses current height, a scored bone age, sex, and growth tempo. Different inputs, different meaning. Neither replaces the other.
A worked example
Take a girl whose mother is 64 inches and father is 70 inches. Mid-parental target height is (64 + 70 - 5) / 2, which is 64.5 inches. You can compute that at the first visit with no imaging.
Bayley-Pinneau needs more. Say the same girl measures 52 inches and radiology returns a bone age of 9.5 years with a delayed pattern. You look up the delayed-tempo girls table at that skeletal age to get her predicted adult height. The two numbers answer different questions, and comparing them is often the clinically interesting part.
Who uses which in clinic
Mid-parental height frames the growth conversation early: is this child tracking toward the family's range? It costs nothing and belongs in the first visit.
Bayley-Pinneau enters once a bone age exists, usually when growth is being formally evaluated. It reflects skeletal maturity, so it moves when tempo does, which mid-parental height cannot see.
Height Predictor implements the Bayley-Pinneau side only. It does not compute mid-parental height, and it does not implement Khamis-Roche or other methods.
The tool for the lookup step
When you already have the scored bone age, Height Predictor on iOS takes the four inputs and returns the table value on device. The calculator guide walks the input flow, and the limitations page covers the method's known error pattern.
Frequently asked questions
Which one is more accurate?
They answer different questions. Mid-parental height estimates genetic potential from parents. Bayley-Pinneau estimates remaining growth from skeletal maturity. Clinicians often look at both and at the gap between them.
Does Height Predictor calculate mid-parental height?
No. The app is a Bayley-Pinneau table lookup from sex, growth tempo, current height, and a scored bone age. Mid-parental height is simple arithmetic you can do without an app.
Can I use Bayley-Pinneau without a bone age?
No. The method starts from a skeletal age that was already scored from a hand radiograph. Without a bone age, mid-parental target height is the tool that works.
Is either method a diagnosis?
No. Both are estimates that inform a growth evaluation. Interpretation stays with the clinician and the published references.
Built around Height Predictor in the Pediatric medicine tools hub.