To study the incidence of chromosomal abnormalities in the umbilical cord blood, and analyze the number and structure and chromosome poly-morphism of the cord blood.

Umbilical cord blood was collected for lymphocyte culture, conventional G-banding and karyotype analysis.

15 500 cases of umbilical cord blood samples were detected, of which 314 cases were abnormal karyotypes, the rate was 2.03%.Chromosomal inversions of children were 220, the percentage in population was 1.42%, the constituent ratio was 70.10%.Chromosomal translocations samples were 41, the percentage in population was 0.26%, the constituent ratio was 13.00%.Chromosome-derived samples were 14, the percentage in population was 0.09%, the constituent ratio was 4.51%.Children with 21-Down Syndrome samples were 12, the percentage in population was 0.08%, the constituent ratio was 3.80%.Children with displaced robertson were 11, the percentage in population was 0.08%, the constituent ratio was 3.50%.In sex chromosome abnormalities, 47, XXX were 5, 47, XXY were 7, 45, X were 4, the percentage in population was 0.10%, the constituent ratio was 5.10%.Children with chromosomal polymorphism were 317, the percentage in population was 2.04%.Compared with the other groups, the chromosomal inversions group′ proportion and constituent ratio were significantly different (χ²=11.53, 15.98; P<0.05). The differences among translocateon, chromosome-derived, 21-Down Syndrome, D-G group and sex chromosome abnormal incidence were not significant (P>0.05), the incidence of abnormal natural of each group was closer.

Karyotype analysis of neonatal umbilical cord blood is a very useful to the insufficient prenatal diagnosis, and important for secondary prevention, fertility and clinical guidlines.