To explore fetal karyotype (FK) of amniotic fluid cells and interventional prenatal diagnosis (IPD) indications of pregnant women in the second trimester with high risk of fetal chromosome abnormality (FCA).

A total of 63 581 pregnant women in the second trimester (19 to 27^{+ 6} gestational weeks) with high risk of FCA who received amniocentesis for FK detection of amniotic fluid cells in Department of Prenatal Diagnosis Center of West China Second University Hospital, Sichuan University from 2014 to 2018 were selected as research subjects. Results of different indications of IPD and fetal karyotype abnormality (FKA) in pregnant women were analyzed retrospectively. The procedures followed in this study complied with the ethical standards of Ethics Committee of West China Second University Hospital, Sichuan University and were approved by the Ethics Committee (Approval No. 077 for Medical Research 2019).

①Among 63 581 pregnant women in the second trimester, detection rate of FKA was 3.13% (1 989/63 581). IPD indications in 63 581 pregnant women included: 25 648 cases of advanced age (age at date of confinement ≥ 35 years old), 29 009 cases were high risk of serological screening, 333 cases were high risk of noninvasive prenatal testing (NIPT), 603 cases were carriers of chromosomal abnormalities in one of the couple, 2 647 cases with fetal structure abnormality and abnormal soft index in ultrasound screening, 1 546 cases were with birth defect history, 7 cases were with abnormal results in FK analysis of amniotic fluid cells in other hospitals, 149 cases were pregnant women with mental retardation or family history of mental retardation, 1 400 cases with a history of adverse exposure to harmful substances during the first trimester, and 2 239 cases were with other indications. And detection rates of FKA in pregnant women with the above IPD indications were 3.26% (836/25 648), 2.04% (593/29 009), 65.17% (217/333), 34.33% (207/603), 3.51% (93/2 647), 1.68% (26/1 546), 85.71% (6/7), 4.03% (6/149), 0.14% (2/1 400), and 0.13% (3/2 239), respectively. ②Among 351 pregnant women whose IPD indications were fetal structural abnormalities in ultrasound screening, the detection rate of FKA in pregnant women with fetal lymphatic cystoma and cutaneous edema was the highest, which was 26.09% (6/23). Among 2 296 pregnant women whose IPD indications were abnormal fetal ultrasound soft indexes, the detection rate of FKA in pregnant women with fetal nuchal translucency (NT) value ≥ 2.5 mm was the highest, which was 7.74% (66/853).

Advanced age, high risk of serological screening and NIPT, carrier of chromosomal abnormalities in one of the couple, fetal structure abnormality and abnormal soft index in ultrasound screening all are indications of IPD for FCA of pregnant women in the second trimester, and the risk of FCA varies with different types of IPD indications. Amniotic fluid cells FK detection by amniocentesis can assess the pregnancy outcomes of pregnant women with IPD indications and provide a reference for reducing birth rate of FKA.