Aneuploidy screening and diagnostic tests
All pregnant women were provided with information about aneuploidy
screening or diagnostic tests. Basic information included the
limitations, test performance and difference between screening and
diagnostic test. The screening tests included MSS and cfDNA screening.
MSS included combined dual, triple, quad, integrated and sequential
tests. cfDNA screening was analyzed for trisomies 21, 18, 13. The
diagnostic tests included chorionic villus sampling and amniocentesis
for conventional karyotyping. Prental chromosomal microarray has not
been used clinically in Korea during this study period. The cfDNA
screening or diagnostic test was recommended when NT was more than 3mm
or 95th percentile, and the diagnostic test was
recommended when fetal structural defects were observed on ultrasound
according to the ACOG guideline [2]. After counseling, participants
selected the first tier test. Based on the first-tier test, we divided
all the participants into three groups: MSS, cfDNA screening, and IT.
When the screening test showed a high risk result, the participants were
counseled about further evaluation. In addition, participants were
offered detailed, high-resolution ultrasound examinations in the second
trimester.