Prenatal ultrasound findings in complete trisomy 9

Abstract

Objective: To report on the prenatal ultrasound findings associated with complete trisomy 9.

Methods: Cases of complete trisomy 9 diagnosed prenatally were identified by reviewing the reports from two large cytogenetics laboratories serving tertiary referral centers for prenatal diagnosis. Information on prenatal ultrasound findings and outcome was obtained in all cases.

Results: Nine cases of complete trisomy 9 were identified. The diagnosis was made in the first trimester in four cases, in the second trimester in three and in the third trimester in two. Two fetuses underwent first-trimester ultrasound screening for aneuploidy and the nuchal translucency thickness was increased in both. All five fetuses detected in the second and third trimesters had several fetal anomalies including Dandy-Walker malformation in four cases, facial dysmorphism in four, genitourinary anomalies in three, congenital heart defects in three, ventriculomegaly in three, abnormal hands in two and megacisterna magna in one. Four fetuses were growth-restricted at the time of ultrasound evaluation. However, the two cases diagnosed in the third trimester had routine second-trimester anomaly scans reported as normal. There were no survivors in this series.

Conclusion: Fetuses with complete trisomy 9 have multiple anomalies that can be readily detected prenatally by ultrasound. These mainly include, but are not restricted to, craniofacial, cardiovascular, musculoskeletal and genitourinary malformations. However, findings can be subtle and therefore missed at the routine second-trimester scan.