Sample collection and ethical approval
Pregnancies were recruited from multiple centers in China for
chorionic-villus sampling, amniocentesis or percutaneous umbilical blood
sampling, between January 2016 and October 2020. Each participant was
subjected to low-pass GS and ultrasonography. Soft markers were
categorized into 12 isolated types, while ultrasonographic anomalies
were categorized into 12 isolated types based on Human Phenotype
Ontology (HPO) terms and the site of anomalies detected by
ultrasonography. Fetuses satisfying any of the following conditions were
included in the study: 1) advanced maternal age (women aged
≥ 35 years) with normal
ultrasonographic results, normal non-invasive prenatal screening
results, normal Down syndrome biochemical screening tests, and no
family/personal history of chromosomal abnormality; 2) ultrasonographic
anomalies (including anomalies in cardiovascular, genitourinary, central
nervous, gastrointestinal, skeletal, facial, or respiratory system,
cystic hygroma, abnormal amniotic fluid, fetal growth restriction, fetal
hydrops, and abdominal wall defect); 3) ultrasonographic soft markers
(including increased nuchal translucency, choroid plexus cysts, absent
or hypoplastic nasal bone, echogenic intracardiac focus, mild
ventriculomegaly, single umbilical artery, mild pyelectasis, aberrant
right subclavian artery, echogenic bowel, short femur/humerus length,
thickened nuchal fold and enlarged cisterna). In total, 43,721 samples
were included in this study. The cohort was divided into three groups by
gestational week: First trimester (11w-13w+6d), Second trimester
(14w-27w+6d), and Third trimester (28w-). Although there was some
overlap between soft markers and anomalies in all trimesters, it had
little influence on the result obtained. This study was approved by the
Ethics Committee of Center for Medical Genetics, Central South
University, Hunan, China. The
ethics application reference numbers were 2015031002 (approval date:
2016.1-2019.12) and 2019-1-23 (approval date: 2019.05-2024.05). All
subjects signed a written informed consent form for genetic
investigation of pregnancy.