Fetal Skeletal Dysplasia (Lethality Prediction)

Step-by-step decision

Choose step by step as prompted; reaching an endpoint gives the management recommendation. You can go back a step or restart anytime.

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Full pathway

1. [Decision] Lethality prediction (FL/AC, thorax) + typing
   Lethality prediction (FL/AC, thorax) + feature typing? (>450 types, few lethal; lethality is mostly from a small chest → pulmonary hypoplasia. First judge lethality, then find features to type. Measure the true femur length (do not measure end-to-end if bowed).)
   • FL/AC <0.16 or thoracic circumference/AC <0.6 or long bones <1st percentile/narrow chest/multiple fractures/cloverleaf skull/hydrops (lethal signs) → Lethal signs · typing + genetics
   • Short long bones but FL/AC ≥0.16, normal thoracic circumference (possibly non-lethal) → Suspected non-lethal · serial monitoring + genetics
2. [End] Lethal signs · typing + genetics
   Lethal signs (FL/AC <0.16, thoracic circumference/AC <0.6, long bones <1st percentile, narrow chest, multiple fractures, cloverleaf skull, hydrops): small chest → lethal pulmonary hypoplasia; skeletal survey + 3D/low-dose fetal CT for typing (thanatophoric dysplasia/achondrogenesis/OI type II) + genetics (FGFR3/COL1A1-2) + genetic counselling; full informed consent.
3. [End] Suspected non-lethal · serial monitoring + genetics
   Short long bones but FL/AC ≥0.16, normal thoracic circumference (suspected non-lethal, e.g. achondroplasia FGFR3 appears late, non-lethal OI): serial monitoring of long bones/thoracic circumference/fractures + skeletal survey + genetics; FL/AC <0.16 with bowing, consider non-lethal OI (measure the true femur length); postnatal pediatric orthopedics/genetics follow-up, planned delivery.

Source guidelines & references

• Fetal skeletal dysplasia lethality prediction (FL/AC <0.16, thoracic circumference/AC <0.6; ACMG/Genet Med guideline)

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

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