gradually in the five groups, and the differences between the groups were statistically significant (P<0.05).The detection rate of pathogenic CNVs in each group increased gradually, and the difference betweengroups was statistically significant (P<0.05). ④ The detection rates of chromosomal karyotype abnormality
between without and with other sonographic abnormalities were statistically significant (14.3% and 43.5%).
The difference between groups was statistically significant (P<0.05). The difference in the detection rate of
pathogenic CNVs between the two groups was statistically significant (17.8% and 50.5%). The difference between
groups was statistically significant (P<0.05). ⑤ After excluded cases with chromosomal abnormalities, the median
value of NT in non-medium-severe thalassemia group was smaller than that in the medium-severe thalassemia
group, there were statistically significant differences between them(P<0.05). A fetus with noonan syndrome
was detected by exome sequencing. Conclusions There were closely relationship between increased NT and
chromosomal abnormalities and monogenic disease. The risk is proportional to the thickness of NT, and the risk
is higher when combined with other ultrasound abnormalities. Prenatal diagnosis is suggested when fetuses with
NT ≥ 3.0 mm, especially for those ultrasonic abnormalities.
2020, Vol. 8 
