Introduction
Birth defects (BDs) are identified in approximately 1 in 300 women who
undergo a routine third trimester ultrasonographic
scan1, and the global prenatal diagnosis rates vary
from 15% to 86%, according to region, BD category, and the method of
diagnosis.2-5 With the rapid development of the
technology for prenatal examinations, a wide range of methods have
become available that improve the prenatal diagnosis of BDs. These
include prenatal ultrasonography, biochemical screening, invasive
techniques such as amniocentesis and chorionic villus sampling (CVS),
non-invasive prenatal testing (NIPT) using cell-free fetal DNA, and gene
diagnose, as well as autopsy.6, 7
The prevalence of multiple birth in China and internationally has been
increasing, such that it is now between 0.9% and 3.3%
worldwide.8-13 This can be, at least in part,
attributed to advancing maternal age and the use of assisted
reproductive technologies (ARTs). The accurate prenatal diagnosis of BD
associated with multiple pregnancy remains challenging, but few studies
have been conducted. Club foot, Down syndrome, and trisomy 18 have been
reported to be less frequently diagnosed in twins than in singleton
fetuses,14-18 whereas Boyle et al. showed that
multiple and singleton pregnancies were associated with comparable rates
of prenatal diagnosis.19 The methods used for prenatal
diagnosis often differ for singleton and multiple pregnancies. For
example, the ultrasonographic survey of general anatomy and
echocardiography for the identification of congenital heart disease are
recommended for twins. However, a prenatal diagnosis of aneuploidy is
commonly made on the basis of the analysis of maternal serum markers,
which is not specific for a particular fetus.18,20 In addition, most previous studies were of small
numbers of twins with specific malformations and used specific screening
methods that can be affected by differences in technical skill level and
up-to-date knowledge.
In Zhejiang, a province located in eastern China, the prevalence of twin
births increased from 2.27% in 2008 to 3.01% in
2013.11 A provincial BD surveillance system has
existed there for over 30 years, and this provides a useful platform for
BD-related researches. In this study, we compared the prenatal diagnosis
of BDs for singleton and multiple pregnancies. We anticipate that the
findings should assist the prenatal diagnosis of BDs, especially in
women with multiple pregnancies.