Prenatal diagnosis of mosaicism for triploidy and trisomy 13

Mosaicism for trisomy 13 and triploidy was detected by amniocentesis perfor med at 18 weeks' gestation because of fetal anomalies. Pregnancy continued and a live-born male was delivered vaginally at 37 weeks. The infant had fe atures common to both trisomy 13 and triploidy: intrauterine growth retarda tion (IUGR), small abnormal ears, cleft palate, and a small jaw. In additio n, he had complete cutaneous syndactyly of fingers 3 and 4 and partial synd actyly of the toes, as seen in triploidy. Mixoploidy for trisomy 13 and tri ploidy was confirmed postnatally in blood, skin, and placenta. Examination of chromosome heteromorphisms and DNA markers suggested the presence of two maternal contributions in the triploid cell line. In addition, the extra c hromosome 13 in the trisomic cell line was derived from the mother. Copyrig ht (C) 2001 John Wiley & Sons, Ltd.