Phenotype-to-Genotype Description of Prenatal Suspected and Postnatal Discovered Upper Limb Anomalies: A Retrospective Cohort Study.

Objective: To evaluate phenotype and genotype characteristics of fetuses and children with upper limb anomalies.

Method: Retrospective cohort study of a prenatal and postnatal cohort with upper limb anomalies from January 2007 to December 2021 in a Fetal Medicine Unit. Prenatally on ultrasound suspected upper limb anomalies, such as transverse and longitudinal reduction defects, polydactyly, and syndactyly, and postnatally identified children referred to the Congenital Hand Team were evaluated separately.

Results: The prenatal group included 199 pregnancies: 64 transverse and 19 longitudinal reduction defects, 103 polydactylies, and 13 cases with syndactyly. The majority of cases with longitudinal reduction defects (n = 10, 52.6%), polydactyly (n = 62, 60.2%), and syndactyly (n = 10, 76.9%) were non-isolated, as opposed to transverse reduction defects, which were generally isolated (n = 41, 64.1%). The postnatal cohort included 362 children with upper limb anomalies with 49 transverse and 22 longitudinal reduction defects, 226 polydactylies, and 65 syndactylies. Chromosomal or monogenic abnormalities were identified in 76/199 (38.2%) cases of the prenatal cohort and in 31/362 (8.6%) cases of the postnatal cohort.

Conclusion: Prenatal identification of minor defects of the digits is a challenge, with more postnatal than prenatal cases. The majority of cases with isolated anomalies in both groups had no underlying chromosomal or monogenic cause, nor were they associated with a syndrome, as compared to the non-isolated cases. Conducting structural anomaly scans and genetic counseling are crucial to assess the risk of genetic abnormalities.