- 1 in 25,000 births.
- Short limbs, short hands and fingers, large head with frontal bossing and depressed nasal bridge, and lumbar scoliosis.
- Limb shortening and typical facial features become apparent >22 weeks’ gestation.
- Detailed ultrasound examination.
- Achondroplasia is due to a mutation in the FGFR3 gene and has autosomal dominant inheritance pattern. The diagnosis can be made by invasive testing or cfDNA analysis of maternal blood.
- Follow-up scans every 4 weeks to monitor growth of the fetal head.
- Standard obstetric care and delivery.
- Cesarean section if the fetal head circumference is >40 cm.
- Homozygotic type: lethal due to severe pulmonary hypoplasia.
- Heterozygotic type: intelligence and life expectancy are normal. Respiratory limitations due to small thorax and development of stenotic vertebral canal (peripheral neurologic deficits) may decrease the quality of life.
- One affected parent: 50%.
- If both parents are affected: 50% risk of heterozygous achondroplasia, 25% risk of homozygous achondroplasia and 25% chance of unaffected child.
- De novo mutation: low recurrence risk.