Prevalence:

• 1 in 10,000 births.
• Most common lethal skeletal dysplasia.

Ultrasound diagnosis:

• Severe shortening of the limbs, narrow thorax, normal trunk length and large head with prominent forehead.
• There are 2 types of thanatophoric dysplasia:
  • Type I (more common): sporadic, the femurs are curved (telephone receiver).
  • Type II (rare): sporadic, the femurs are straight but the skull is cloverleaf-shaped.

Investigations:

• Detailed ultrasound examination.
• Thanatophoric dysplasia is due to a mutation in the FGFR3 gene. The diagnosis can be made by invasive testing or cfDNA analysis of maternal blood.

Follow up:

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

Delivery:

• Standard obstetric care and delivery.
• Pregnacies are often complicated by polyhydramnios, prematurity, malpresentation and cephalopelvic dysproporion. The presence of the cloverleaf deformity and hydrocephalus may require cephalocentesis and assisted delivery.

Prognosis:

• The condition is lethal due to severe pulmonary hypoplasia.

Recurrence:

• No increased risk.