THE CLINICAL IMPORTANCE OF PERICENTRIC-INVERSION OF CHROMOSOME-9 IN PRENATAL-DIAGNOSIS

Objective: Pericentric inversion is a structural chromosomal variant t hat occurs frequently in the human population and usually has no pheno typic effect. Pericentric inversion of chromosome 9 is the most common type of inversion, with an overall incidence of 1.98%, especially in African-Americans. Therefore, this study was undertaken to examine a r elatively large database of predominantly African-Americans to determi ne the incidence of inversion of chromosome 9 and to assess the perina tal outcomes of such fetuses. Methods: We have reviewed the results of 652 cytogenetic studies on mid-trimester amniocentesis (16-18 weeks) during a 10-year period from January 1985 to February 1995. Results: O f 652 patients reviewed, pericentric inversion of chromosome 9 was fou nd in 27 cases giving an incidence of 4.1%. The indications for amnioc entesis among these 27 patients included advanced maternal age (16/27; 59.3%), abnormal ultrasound findings (5/27; 18.5%), abnormal maternal serum screening tests (4/27; 14.8%), and family history of an abnorma l child (2/27; 7.4%). Immediate neonatal evaluation of these infants w as normal in 23 (88.9%) and abnormal in 3 (11.1%); one had a low Apgar score at 1 and 5 min, one had bilateral capillary hemangioma over the eyelids, and one had heart murmur and an irregular cardiac rhythm. Mo st of the patients (24/27) were multigravida, nine of whom had a histo ry of two or more previous spontaneous abortions. Conclusions: These d ata support the clinical reports that inversion of chromosome 9 is ass ociated with a normal outcome in the majority of cases.