**8.1. Micrognathia-retrognathia**

Prevalence: 1: 1500 births.

**Ultrasound diagnosis:** Subjective finding of prominent upper lip and receding chin in the mid-sagittal view of the face (**Figure 18**). These findings might be due to micrognathia (short mandible) or retrognathia (backward displacement of the mandible). Severe micrognathia is associated with polyhydramnios (>25 weeks gestation), due to glossoptosis (normal tongue obstructing small oral cavity).

**Associated abnormalities:** Chromosomal abnormalities, mainly trisomy 18 and triploidy, are found in about 30% of cases. Any one of >50 genetic syndromes are found in most fetuses. Micrognathia is usually associated with >50 genetic syndromes, including Pierre-Robin anomaly, Treacher Collins syndrome, otocephaly [59].

**Investigations:** ultrasound including echocardiography, karyotyping and array.

**Follow up:** Ultrasound scans every 4 weeks to monitor growth and amniotic fluid.

**Delivery:** In hospital with facilities for neonatal intensive care, while a pediatrician is present in the delivery room and be prepared to intubate the neonate.

**Prognosis:** Neonatal mortality >80% due to associated abnormalities. In Pierre–Robin anomaly, the survival rate is good.

**Recurrence:** Genetic syndromes: 25–50%. Trisomies: 1%. Isolated: no increased risk of recurrence.
