Retrospective analysis of genetic etiology and obstetric outcome of fetal cystic hygroma: A single-center study

Cystic hygroma (CH) is a relatively common observation in prenatal ultrasounds; however, there are few studies about copy number variations (CNVs) of fetuses with CH. METHODS: We performed a retrospective analysis on 40 pregnant patients (out of 8000 pregnant patients) whose fetuses had CH from November 2016 to June 2021. Villus, amniotic fluid, or umbilical cord blood samples were collected, based on the corresponding gestational age, for karyotype analysis and single-nucleotide polymorphism array (SNP-array). RESULTS: Among the 40 fetuses with CH, 16 (40.0%, 16/40) exhibited isolated CH and 24 (60.0%, 24/40) exhibited CH combined with other ultrasound abnormalities. The most common CH-comorbid ultrasound abnormalities observed in this study were congenital heart disease (25.0%, 6/24), thickened nuchal translucency (20.8%, 5/24), and fetal edema (12.5%, 3/24). Karyotype and SNP-array analysis resulted in an overall detection rate of 30.0% (12/40). Karyotype analysis led to the detection of eight cases of pathogenic CNVs, among which 45, X was the most common. In addition to the above pathogenic CNV, four additional cases were detected by SNP-array. There was no significant difference in the observed pathogenic CNVs between isolated CH and CH combined with other ultrasound (31.3% vs 29.2%, P > .99). Karyotype analysis and SNP-array results influence whether parents terminate the pregnancy. When genetic abnormalities are detected in the fetus, the parents often choose to terminate the pregnancy. CONCLUSIONS: Our study emphasizes that genomic examination should be performed on fetuses with CH to confirm the etiology as soon as possible. During genetic counseling, all fetal characteristics should be carefully and comprehensively evaluated.