Amniocentesis is a prenatal diagnostic procedure in which a small amount
of amniotic fluid is withdrawn from the sac surrounding the fetus for
testing. It has been a conventional method of obtaining fetal genetic
information since the late 1960s1. It is traditionally
performed between 16-24
gestational weeks in
China,
and it provides pregnant women and their families with an opportunity
for early diagnosis of and appropriate intervention for the undesirable
findings2.
Nowadays, clinically available methods for analyzing fetal genetic
information from amniotic fluid include traditional karyotyping,
chromosomal
microarray analysis (CMA), medical exome sequencing (MES), whole-genome
sequencing (WGS) and
whole-exome
sequencing (WES). The detection ranges of them are different which
result in different detection rates and costs. For example, compared
with traditional karyotyping, CMA
provides
more genetic information of the fetus and has demonstrated to increase
the diagnostic yield by 5-9% 3, 4. Consistently,
5.3% fetuses with late-appearing
abnormal
ultrasound findings and normal karyotype results showed pathogenic CMA
results. Owing to its higher detection rate, shorter turnaround time,
and affordable expense, CMA fleetly
became
the
first-tier
method in prenatal diagnosis associated with the occurrence of fetal
structural anomalies and/or increased nuchal translucency (NT)1.
Clinical
implementation of next-generation sequencing (NGS) in field of prenatal
diagnostics are widely available. Petrovski and co-workers noted that
patients underwent WES by NGS had higher diagnostic yields (25–35%)
among fetuses with genetic disorders, while negative findings were
observed by either karyotyping or CMA techniques 5, 6.
Although
both WGS and WES can detect novel pathogenic
genes,
WGS analyzes the entire genome while WES and MES focus only on the exons7, 8. Since the exons generally have greater clinical
relevance and applicability to human diseases, WES and MES were more
frequently used in prenatal
diagnosis.
The
chances of late-appearing abnormal ultrasound findings after a normal
fetal-targeted organ scan before 24 gestational weeks are estimated at
5.5%-17% 9, 10. Late amniocentesis can be performed
after 24 gestational weeks onwards which is considered to be safe and
effective1. However, though it is associated with a
higher risk of miscarriage than amniocentesis11,
cordocentesis is still widely employed as the method of choice for
prenatal diagnosis after 24 weeks in China. Clinical data remains
lacking regarding the incidence, indications, complications, and
outcomes associated with late amniocentesis. The aim of this
retrospective study was to provide more detailed clinical data
associated with late amniocentesis procedures in prenatal diagnosis.