Chromosomal Inversions in Prenatal Diagnosis and Their Clinical Significance

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American Journal of Obstetrics and Gynecology







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Objective To assess the frequency of familial versus de novo chromosome inversionsduring prenatal diagnosis and determine their clinical significance. Study Design A retrospective analysis of prenatally diagnosed inversions from a large reference lab database was performed. The data was reviewed for the type and frequency of various types of inversions, as well as their inheritance pattern. Variant inversion 9 was excluded. Results A total of 4088 (0.3 %) inversions were identified in a data set of 1.3 million invasive diagnostic procedures. Pericentric inversions accounted for 73% of the inversions (n=2987), and the remaining 27% were paracentric. Common inversions involving chromosomes 1, 2, 10, and Y accounted for 46.7% of the total inversions (1911/4088). The most frequently identified inversion was inversion 2, inv2(p11q13), accounting for 23% of all inversions. The indications for invasive testing were as follows: advanced maternal age 1941 (47.5%), abnormal aneuploidy screen 935(22.9%), abnormal ultrasound findings 617(15%), previous chromosomal abnormality 449(11%), family history of a significant genetic disorder 69(1.7%), other indication 68(1.7%), and no indication in 10 cases. Excluding the common inversion group, mode of inheritance was available in 81% of cases (1767/2177), with 92% of inversions being inherited (1633/1767). There was a slight preponderance of maternal inheritance (53%). When an abnormal ultrasound was the indication for testing, familial inversions accounted for 95% of cases, which was similarly seen in other groups. Conclusion Prenatally diagnosed chromosome anomalies present counseling challenges. Our study shows that over 90% of prenatally diagnosed inversions have familial inheritance for both the common and uncommon inversions, and are therefore of no clinical significance. This information can help alleviate anxiety during prenatal counseling. Parental chromosome analysis is important in cases where an inversion is diagnosed. Non-familial inversions may be due to non-paternity, gonadal mosaicism, or de novo, and further testing with microarray may be helpful to appropriately counsel these patients.


Obstetrics and Gynecology



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