Prevalence:

• 1 in 40,000 births.
• Second most common lethal skeletal dysplasia, after thanatophoric dysplasia.

Ultrasound diagnosis:

• Severe shortening of the limbs, narrow thorax, short trunk length and large head.
• Associated with micrognathia, nuchal edema and polyhydramnios.
• There are 2 types of achondrogenesis:
  • Type I (20%): autosomal recessive; there is poor mineralization of the skull and vertebral bodies, as well as rib fractures.
  • Type II (80%): sporadic; there is poor mineralization of the vertebral bodies but not the skull and there are no rib fractures.  

Investigations:

• Detailed ultrasound examination.
• Achondrogenesis is due to mutations in SLC26A2, COL2A1 and TRIP11 genes.

Follow up:

• If pregnancy continues, follow-up should be standard.

Delivery:

• Standard obstetric care and delivery.

Prognosis:

• The condition is lethal due to severe pulmonary hypoplasia.

Recurrence:

• Type I: 25%
• Type II: no increased risk.