Beyond the Negative: Insights From Postnatal Medical Genetics Follow-Up After Nondiagnostic Prenatal Exome Sequencing

To evaluate postnatal medical genetic reassessment and reinterpretation of prenatal exome sequencing (pES) in liveborn children with prenatally identified structural anomalies and nondiagnostic prenatal genetic testing.

We performed a retrospective chart review of 61 liveborn children with fetal structural anomalies who had nondiagnostic chromosomal studies and pES at a tertiary care center in British Columbia, Canada (2016-2022). We assessed postnatal medical genetics reassessment, clinical drivers of reassessment, and outcomes of selective pES reinterpretation.

Postnatal medical genetics reassessment occurred in 41% (25/61) of children. Most reassessments occurred in the neonatal intensive care unit within the first week of life (68%, 17/25) and were prompted by postnatal phenotype modifications in 44% (11/25). Additional clinical drivers prompting reassessment included prenatally identified variants of uncertain significance and prenatal phenotypes of multisystem structural anomalies or unexplained hydrops. Of the children reassessed postnatally, 44% (11/25) underwent pES reinterpretation. Explanatory genetic diagnoses following reassessment and pES reinterpretation were made in 27% (3/11), representing 12% (3/25) of those reassessed and 5% (3/61) of the cohort. One additional postnatal genetic diagnosis was made, which explained a portion of the postnatal phenotype but was not considered explanatory for the prenatal findings.

Postnatal pES reinterpretation identified genetic diagnoses in carefully selected cases following medical genetics reassessment of children with nondiagnostic prenatal testing for fetal structural anomalies, supporting a structured, clinically guided approach to postnatal follow-up.