Next-Generation–Sequencing-Based Noninvasive Prenatal Diagnosis - Next Generation Sequencing Technologies in Medical Genetics - page 41

Chapter 5
Next-Generation-Sequencing-Based
Noninvasive Prenatal Diagnosis

5.1 Introduction

Prenatal diagnosis is important part of obstetric practice (Tounta et al. 2011 ).
Traditionally, fetal DNA is obtained by invasive techniques, namely, amniocentesis
and chorionic villus sampling. Such invasive procedure leads to a miscarriage rate
of about 1 % and is reserved only for high risk pregnancies for specifi c genetic con-
ditions which include fetal chromosomal aneuploidies and monogenic disorders
with relatively high prevalence in the relevant populations. The ultimate goal for
early prenatal diagnosis, while decreasing the miscarriage rate, is to employ nonin-
vasive testing using maternal peripheral blood as a source of fetal genetic material
(Tounta et al. 2011 ). Multiple studies indicate that both intact fetal cells and cell-
free fetal nucleic acids (cffNA) cross the placenta and can be found in the maternal
circulation. Intact fetal cells present an attractive target for noninvasive prenatal
diagnosis (NIPD) of fetal chromosomal abnormalities (Lo et al. 1996 ). Isolation and
analysis of fetal cells from maternal circulation have been extensively investigated
and several methods for fetal cell enrichment have been developed (Bianchi 1999 ;
Jackson 2003 ; Sekizawa et al. 2007 ). However, due to the lack of cells in the mater-
nal circulation and low effi ciency of enrichment methods results have not been
promising. In addition, it has been challenging to perform Fluorescent In Situ
Hybridization (FISH) because of the presence of apoptotic nuclei of fetal cells
(Bianchi et al. 1997 ).
In 1997, Lo et al. reported the presence of cell-free fetal DNA (cffDNA) in
maternal plasma and serum in amounts signifi cantly increased, as compared to fetal
DNA extracted from the cellular fraction of maternal blood (Lo et al. 1997 ). This
discovery rapidly paved the way for the detection of paternally inherited alleles in
maternal blood, including, most notably, Rh D blood group, fetal sex, and single-
gene disorders. For more than a decade now, NIPD has been used routinely for
pregnancies in which paternally inherited alleles require detection because their
inheritance would indicate a clinical condition, such as hemolytic disease of the
fetus and newborn, congenital adrenal hyperplasia, and hemophilia (Avent et al.