- 1 in 1,500 births.
- Subjective finding of prominent upper lip and receding chin in the mid-sagittal view of the face. These findings may 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).
- Chromosomal abnormalities, mainly trisomy 18 and triploidy, are found in about 30% of cases.
- Associated with >50 genetic syndromes, including:
- Pierre–Robin anomalad: micrognathia or retrognathia, cleft palate and glossoptosis. In half of cases this a sporadic isolated finding and in the other half it is associated with other anomalies or with recognized genetic and non-genetic syndromes).
- Treacher Collins syndrome: autosomal recessive or autosomal dominant with 60% de novo mutations; hypoplasia of the maxilla and zygomatic bone, micrognathia, cleft palate and malformed or absent ears.
- Otocephaly: sporadic: severe micrognathia or agnathia, and mid-line defects, including holoprosencephaly, anterior encephalocele, cyclopia, aglossia, and mid-facial location of the ears.
- Detailed ultrasound examination.
- Invasive testing for karyotyping and array.
- Ultrasound scans every 4 weeks to monitor growth and amniotic fluid.
- Place: hospital with facilities for neonatal intensive care.
- Time: 38 weeks.
- Method: induction of labor aiming for vaginal delivery. A pediatrician should be present in the delivery room and be prepared to intubate the neonate.
- Neonatal mortality: >80% due to associated abnormalities.
- In Pierre–Robin anomalad survival is good.
- Isolated: no increased risk of recurrence.
- Part of trisomies: 1%.
- Part of genetic syndromes: 25% to 50%.