Fetal micrognathia in the first trimester: An ominous finding even after a normal array

Area of Science:

• Prenatal diagnosis
• Fetal medicine
• Medical genetics

Background:

• Micrognathia, a condition characterized by an abnormally small jaw, can be detected during early pregnancy.
• First-trimester diagnosis of micrognathia presents unique challenges in determining prognosis.
• Nuchal translucency screening is a key point for identifying potential cases.

Purpose of the Study:

• To assess the prognosis of fetuses diagnosed with micrognathia in the first trimester.
• To understand the genetic underpinnings and associated anomalies in early-diagnosed micrognathia.
• To guide clinical management and counseling for pregnancies with first-trimester micrognathia.

Main Methods:

• Retrospective review of 43 pregnancies with first-trimester micrognathia diagnosed during nuchal translucency screening.
• Analysis of maternal demographics, sonographic findings, and pregnancy outcomes.
• Utilized chromosomal microarray and whole-exome sequencing for genetic investigations.

Main Results:

• Seven cases (16.3%) showed chromosomal abnormalities.
• Whole-exome sequencing identified monogenic syndromes in 8 out of 13 investigated fetuses (61.5%), including de novo dominant and recessive conditions.
• In cases where whole-exome sequencing was declined (23 cases), 10 (43.5%) had additional anomalies detected on later anatomic ultrasounds.

Conclusions:

• An apparently isolated micrognathia in the first trimester warrants careful evaluation, even with a normal chromosomal microarray.
• The likelihood of an underlying genetic syndrome or additional anomalies is significant and impacts the overall prognosis.
• Comprehensive genetic testing and detailed follow-up scans are essential for accurate diagnosis and management.