ID-5184 Wonca Abstracts supplement A-K 13-10-23 - Flipbook - Page 219
WONCA 2023 Supplement 1: WONCA 2023 abstracts (A–K)
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Non-invasive prenatal screening: Making it work in
your practice
Dr Melanie Galea
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Sonic Healthcare Education
Non-invasive prenatal testing (NIPT) involves whole-genome sequencing of cell-free DNA (cfDNA)
fragments derived from maternal peripheral whole blood samples to screen for common chromosome
disorders in singleton and twin pregnancies that can affect the health of a baby (ie Down syndrome
[trisomy 21], Edwards syndrome [trisomy 18] and Patau syndrome [trisomy 13]). The standard NIPT
can also screen for common disorders of the sex chromosomes (ie Turner syndrome [45,X], Klinefelter
syndrome [47,XXY], triple X syndrome [47,XXX] and XYY syndrome [47,XYY]) in singleton pregnancies.
Genome-wide NIPT (gNIPT) has more recently become available and is sought by both patients and
clinicians who wish to obtain additional information related to a given pregnancy. While the positive
predictive value (PPV) of the genome-wide screen for rare autosomal trisomies (13%) and segmental
copy number variants is substantially lower (10–30%) than for the common trisomies (37–92%; PMID
35608568), there is growing evidence in the literature that the use of the genome-wide component can
increase the detection of fetal anomalies, and pregnancies associated with poor prognosis, intrauterine
growth restrictions, malformations and adverse fetal outcomes (PMIDs 28855395, 27362910,
25585704, 29956348). In the context of a busy general practice, the challenge lies in providing
sufficient information about the purpose, scope and outcomes of different non-invasive screening
options, as well as in dealing with high-risk results.
There is a strong international move to reproductive carrier screening:
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American College of Medical Genetics and Genomics: ‘All pregnant patients and those planning a
pregnancy should be offered Tier 3 carrier screening’ (>100 gene screen).
American College of Obstetricians and Gynecologists: ‘Information about carrier screening
should be provided to every pregnant woman. Carrier screening and counseling ideally should be
performed before pregnancy because this enables couples to learn about their reproductive risk
and consider the most complete range of reproductive options’.
The European Society of Human Genetics has reviewed the need for education among health
practitioners about the science of carrier screening and the challenges in ensuring couples make
informed choices about carrier screening.
In India, the proportion of congenital abnormalities that can be attributed to genetic disorders
is rising as the proportion due to malnutrition and infectious diseases is falling. As a result,
there is growing interest in the role of carrier screening in reducing the incidence of congenital
malformations.
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