Genetic analysis in fetuses with isolated clubfoot: diagnostic insights and added value

This study evaluates the diagnostic genetic yield in fetuses prenatally suspected with sonographically isolated clubfoot. We conducted a retrospective study on all fetuses with apparently isolated clubfoot on initial ultrasound at Amsterdam UMC between January 2021 and December 2024. Clubfoot was classified as isolated when no additional structural anomalies were observed on initial imaging. Among 218 total cases of clubfoot, 140 (64%) were classified as isolated. Prenatal genetic testing was performed in 64 of these cases (46%), of whom 61 (95%) underwent both copy number variant (CNV) and single nucleotide variant (SNV) analysis. In 38 of the 61 (62%) cases targeted investigation of the DMPK gene was carried out. (Likely) pathogenic causative variants were identified in six of the 61 (9.8%) pregnancies, being two of the 26 tested (7.7%) of unilateral clubfoot and four of the 35 tested (11.4%) bilateral clubfoot. These include SNVs in TRPV4 , PTPN11 , BBS2 , and MED13 (4/61 = 6.6%) and two CNVs, a de novo 22q11.23 deletion, and a de novo 5q21.1q31.1 deletion (2/61 = 3.3%). One case remained unsolved due to the identification of a Variant of Uncertain Significance in PIEZO2 , and three cases revealed non-causative variants, so-called unsolicited findings. These findings highlight the diagnostic yield of prenatal CNV- and SNV-testing in cases of suspected isolated clubfoot, but does not support systemic testing for DMPK . While broad genetic testing may aid in diagnosis and counseling, challenges persist regarding interpretation, unsolicited findings, and clinical utility in guiding reproductive decisions.