摘要
Fetal chromosomal aneuploidies can lead to fetal loss and major birth defects.The best known chromosomal aneuploidy is Down syndrome,or medically termed trisomy 21,where the affected individual has an extra full or partial copy of chromosome 21.The extra copy of genetic material is the culprit for causing developmental problem for affected individuals.Three types of Down syndrome exist:trisomy 21 accounts for 95%of cases,translocation accounts for about 4%and mosaicism accounts for about 1%.Less common chromosomal aneuploidies include Edward syndrome(trisomy 18),Patau syndrome(trisomy 13),Turner syndrome(45,X),Klinefelter syndrome(47,XXY),and 47,
Fetal chromosomal aneuploidies can lead to fetal loss and major birth defects.The best known chromosomal aneuploidy is Down syndrome,or medically termed trisomy 21,where the affected individual has an extra full or partial copy of chromosome 21.The extra copy of genetic material is the culprit for causing developmental problem for affected individuals.Three types of Down syndrome exist：trisomy 21 accounts for 95%of cases,translocation accounts for about 4%and mosaicism accounts for about 1%.Less common chromosomal aneuploidies include Edward syndrome（trisomy 18）,Patau syndrome（trisomy 13）,Turner syndrome（45,X）,Klinefelter syndrome（47,XXY）,and 47,
