Two cases of prenatally diagnosed trisomy 18 presenting with rarely seen anomalies

Objective: Trisomy 18 syndrome is the second most common autosomal trisomy syndrome. More than 130 different fetal anomalies have been reported in this syndrome. Usually fetuses with trisomy 18 present with multiple anomalies.  But sometimes atypical presentations of the syndrome can be possible. Radius aplasia is a very rare condition which can be a part of this syndrome; it can be helpful for prenatal diagnosis. Cardiac anomalies can be seen in over90% of trisomy 18 fetuses. The most common cardiac anomalies seen in this syndrome are atrial septal defects, ventricular septal defects, left heart anomalies and valvular anomalies. Rarely double outlet right ventricle can be seen with this syndrome too. Cases: The first case was a patient at the 17th week of her pregnancy. During second trimester ultrasonographic scan bilateral radius aplasia was the only ultrasonographic abnormal finding.The second case was a patient at the 23th week of her pregnancy. The fetus had omphalocele, umbilical cord cyst and double outlet right ventricle. Chromosomal analysis of these two patients detected fetuses with trisomy 18. Conclusion: Antenatal diagnosis is important in cases of trisomy 18 who have poor prognosis for survival. Trisomy 18 must always be in mind in cases of radius aplasia and in any kind of cardiac malformations. Key words: Trisomy 18; radius aplasia; double outlet right ventricle