孕前基因檢查

Hello

Are you referring to non-invasive prenatal testing for the fetus?

I have taken for your reference an abstract from the RCOG Scientific Impact Paper No. 15
March 2014

‘Fetal genetic testing and aneuploidy diagnosis have until recently both needed invasive diagnostic
sampling procedures carrying a small but significant risk of miscarriage. In 1997 the presence of cell-free
fetal DNA (cffDNA) in the maternal circulation was reported.1 Fetal DNA comes from the placenta,2 can
be detected from the first trimester of pregnancy onwards3 and is rapidly cleared from the maternal
circulation after delivery.4 Maternal blood is therefore a reliable source of material for prenatal diagnosis.
However, the cffDNA is mixed with a larger proportion of maternal cell-free DNA and current
methodologies do not allow complete separation of fetal from maternal DNA in vitro. Therefore, the
first applications of this phenomenon focused on the detection, or exclusion of, paternally-inherited fetal
DNA sequences that are not present in the mother, such as Y chromosome sequences in pregnancies with
a male fetus or rhesus D (RhD) sequences in women who are RhD-negative. Recently, DNA sequencing
technologies have allowed very precise relative quantification of DNA fragments and so the detection of
the extra material resulting from fetal chromosome trisomy within the maternal plasma DNA can now
be performed in a robust manner.’

‘Non-invasive prenatal testing NIPT using maternal plasma DNA is available for several conditions. Obstetricians have used NIPT to guide management of women who are RhD-negative and whose fetuses are at risk of HDFN for many
years and guidelines should already reflect this change in practice. Fetal sex determination for clinical
indications in pregnancies at high sex-linked genetic risk is also established practice. Testing for
aneuploidy and especially Down syndrome by maternal plasma MPS is now available commercially but
while the test result is much more accurate than existing screening strategies, it is still not a diagnostic
assay. Hence, the term ‘non-invasive testing’ is currently used.’

These NIPT tests are available in the private clinics in Hong Kong.

Cheers,