To explore the application of interventional karyotype examination combined with ultrasound in the diagnosis of fetal chromosome aneuploidy detected by the noninvasive prenatal test (NIPT).

Forty-two cases with abnormal NIPT results were enrolled from October 2015 to December 2017 in prenatal diagnosis center of Xuzhou Center Hospital. Further invasive prenatal examinations such as amniotic fluid or cord blood puncture were accomplished for the definite diagnosis. Conventional Giemsa (G) banding karyotype analyses were conducted for the fetus and parents and all cases were followed for pregnancy outcomes. Comparison of the efficiency of interventional karyotype test and NIPT in the detection of fetal chromosomal abnormalities was made by McNemar χ² and Kappa consistency tests.

Of the 42 cases with abnormal NIPT results, 31 had autosomal abnormalities, 10 had sex chromosome abnormalities, and 1 had both autosomal and sex chromosome abnormalities. The autosomal abnormalities included 17 cases at high risk for 21-trisomy, 9 cases at high risk for 18-trisomy, and 1 case each of 7-trisomy, 15-trisomy, 13-trisomy, chromosome 7 with 51Mb repeated segment, and chromosome 16 with abnormality. The sex chromosome abnormalities included 6 cases of 45, XO, 2 cases of 47, XYY, and 1 case each of chromosome 47, XXX and 47, XXX with XX. Of the 42 patients, 1 gave up prenatal diagnosis and selected induction of labor, 36 underwent amniocentesis, and 5 underwent umbilical vein puncture. Finally, 14 cases of 21-trisomy, 7 cases of 18- trisomy, and 1 case of 47, XYY were diagnosed. Among the 14 definite cases of 21-trisomy, 12 were complicated with ultrasound structural abnormalities, while the 7 definite cases of 18-trisomy had totally ultrasound structural abnormalities. The other cases showed no abnormalities in the chromosomes of 320-400 bands and had no ultrasound structure changes. A total of 22 cases underwent induced labor, 1 case had abortion, and the other 19 cases were followed with good neonatal outcomes. Therefore, the positive rate of fetal chromosome abnormality detected by the NIPT was significantly higher than that by interventional karyotype examination (P<0.05).

NIPT has a high detection rate for 21-trisomy and 18-trisomy, but there are still false positives for autosomal and sex chromosomes. Fetal structure ultrasound and interventional karyotype examination are still necessary for pregnant women with abnormal NIPT results to avoid harm to innocent fetuses.