Table 3. Incidence of chromosomal defects in fetuses with increased nuchal translucency thickness.

Chromosomal aberrations	Case number	Proportion (%)
1. Autosomal aneuploidy	399	71.3
Triploidy	1	0.2
Trisomy 21	302	53.9
Trisomy 18	68	12.1
Trisomy 13	19	3.4
Mosaicism	2	0.4
Other chromosomes	7	1.3
2. Sex aneuploidies	35	6.2
45, X	13	2.3
47, XXY	3	0.5
47, XXX	7	1.3
47, XYY	4	0.7
Mosaicism	8	1.4
3. Structural rearrangements	125	22.5
Reciprocal translocation	9	1.6
Robertsonian translocation	15	2.7
Der translocation	5	0.9
Inversion	16	2.9
Deletion	5	0.9
Duplication	0	0.0
Insertion	4	0.7
Marker chromosomes	2	0.4
Polymorphism	58	10.4
Mosaicism	11	2.0
Total	560	100