POSTNATAL CONFIRMATION OF PRENATALLY DIAGNOSED TRISOMY-16 MOSAICISM IN 2 PHENOTYPICALLY ABNORMAL LIVEBORNS

Two phenotypically abnormal liveborns in whom trisomy 16 mosaicism was diagnosed prenatally by amniocentesis are described. Analysis of a pe rcutaneous umbilical blood sample in one case revealed a normal chromo somal complement. Ultrasound examinations performed at the time of amn iocentesis were normal. Serial sonography during the late second and t hird trimesters demonstrated progressive intrauterine growth retardati on (IUGR) in both fetuses and a cardiac defect in one. At birth, both infants had dysmorphic features and multiple congenital anomalies. Tri somy 16 mosaicism was confirmed postnatally in both infants in skin fi broblasts; however, peripheral blood samples contained only chromosoma lly normal cells. The two mosaic trisomy 16 cases described in this re port, together with the five confirmed cases reported previously, demo nstrate the need for caution in the counselling of patients when triso my 16 mosaicism is diagnosed prenatally in amniotic fluid samples. Suc h cases potentially can result in the birth of dysmorphic infants with significant birth defects, growth retardation, and possible developme ntal disabilities.