Trisomy 21 and Ebstein Anomaly. M.J. Huggins, J. Mernagh, J. Xu, M.J.M. Nowaczyk. Hamilton Health Sci Corp, Hamilton, ON, Canada.

   Ebstein anomaly (EA) consists of downward displacement of an abnormal tricuspid valve into the right ventricle with resultant enlargement of the right atrium and tricuspid valve incompetence. Although there are reports of EA following fetal exposure to lithium, EA malformation is sporadic and rare. Approximately 40 per cent of fetuses and children with Down syndrome (DS) have a cardiac anomaly; there are two cases of EA and DS reported in the literature. We report a fetus with trisomy 21 who had EA diagnosed during a prenatal sonographic evaluation at 25 weeks of gestation. This finding was confirmed by fetal echocardiography.
   A 42 year old G1 was referred for a genetic amniocentesis because of advanced maternal age and triple screen positive for DS. The fetal karyotype was 47,XY,+21. Sonographic examination at 25 weeks of gestation showed thickening of the nuchal fold measuring 10.5 mm (normal <6 mm), and cerebral ventriculomegaly [posterior horns of the cerebral ventricles measured 11 mm in maximum diameter (normal<10 mm)]. The fetal heart circumference was 106 mm corresponding to an estimated gestation of 29 weeks. The right atrium was enlarged with an apically displaced tricuspid valve. The interventricular septum was intact. Fetal echocardiogram confirmed the finding of EA. Bilateral pleural effusion was also noted. The pregnancy ended at 33 weeks of gestation following the ultrasound finding of intrauterine fetal demise. Autopsy was not performed.
   To our knowledge, EA has previously been reported in association with DS in two patients; in both cases EA was an incidental finding and had no clinical sequelae. These three cases suggest that DS should be considered in the differential diagnosis of EA detected antenatally.