Chromosomal Abnormality in Fetuses with Isolated Antenatal Hydronephrosis: Update for Prenatal Diagnosis and Genetic Counseling

Abstract Background: The prenatal finding of fetuses with antenatal hydronephrosis (ANH) gives a significant dilemma for the clinicians. Which patients require invasive prenatal diagnosis? Though previous literatures have recommended the use of chromosomal microarray analysis (CMA)for fetuses with CAKUT, the cutoff value for CMA have no current consensus on fetuses with ANH. In this article, we aimed to detect chromosomal abnormalities in fetuses with isolated severe ANH (anterior-posterior renal pelvic diameter (APRPD) ≥ 10mm) by CMA, summarized the literatures and proposed recommendations for the prenatal genetic diagnosis according to APRPD.Methods: Fetuses (n=84) with isolated severe ANH (APRPD ≥ 10mm) were evaluated by CMA. According to APRPD measurements at second trimester, we classified the cases into two groups: (1) Group A: cases with APRPD of 10–15 mm(N=57); (2) Group B: cases with APRPD ≥ 15 mm(N=27).The prenatal and postnatal outcomes were assessed by ultrasonic examination and telephone follow-up.Results: Overall, one case with 18 trisomy was identified. Clinically significant copy number variants (pathogenic or likely pathogenic CNVs) were identified in 11.9% (10/84) cases, including 3.5% (3/84) of pathogenic CNVs. The detection rates were 5.2% (3/57), 25.9% (7/27) for group A and group B, respectively. There was statistically significant differences in the frequency of clinic significant CNVs in the two groups (p＜0.05). Conclusion: CMA is valuable in prenatal genetic diagnosis of fetuses with severe ANH（APRPD ≥ 10mm）, regardless of whether other ultrasonic abnormalities were observed. This cohort should be followed up during the pregnancy.