Non-Invasive Prenatal Testing

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Educational Use Only - Embryology is an educational resource for learning concepts in embryological development, no clinical information is provided and content should not be used for any other purpose.

Introduction

Trisomy 21 karyotype cartoon

Non-Invasive Prenatal Testing (NIPT) is a new technique that analyzes cell-free fetal DNA circulating in maternal blood.

There are other pages that refer to postnatal diagnostic testing. (More? Neonatal Diagnosis)


This Embryology site is a developmental educational resource, it does not provide specific clinical details, you should always refer to a health professional.


Diagnosis Links: Prenatal Diagnosis | pregnancy test | amniocentesis | chorionic villus sampling | ultrasound | Alpha-Fetoprotein | Pregnancy-associated plasma protein-A | Fetal Blood Sampling | Magnetic Resonance Imaging | Computed Tomography | Non-Invasive Prenatal Testing | Fetal Cells in Maternal Blood | Preimplantation Genetic Screening | Comparative Genomic Hybridization | Genome Sequencing | Neonatal Diagnosis | Category:Prenatal Diagnosis | Fetal Surgery | Classification of Diseases | Category:Neonatal Diagnosis

| Assisted Reproductive Technology | In Vitro Fertilization | Journal - Prenatal diagnosis

Some Recent Findings

  • Noninvasive Prenatal Testing: The Future Is Now[1] "Prenatal detection of chromosome abnormalities has been offered for more than 40 years, first by amniocentesis in the early 1970s and additionally by chorionic villus sampling (CVS) in the early 1980s. ...The ability to isolate fetal cells and fetal DNA from maternal blood during pregnancy has opened up exciting opportunities for improved noninvasive prenatal testing (NIPT). Direct analysis of fetal cells from maternal circulation has been challenging given the scarcity of fetal cells in maternal blood (1:10,000-1:1,000,000) and the focus has shifted to the analysis of cell-free fetal DNA, which is found at a concentration almost 25 times higher than that available from nucleated blood cells extracted from a similar volume of whole maternal blood. There have now been numerous reports on the use of cell-free DNA (cfDNA) for NIPT for chromosomal aneuploidies-especially trisomy (an extra copy of a chromosome) or monosomy (a missing chromosome)-and a number of commercial products are already being marketed for this indication. This article reviews the various techniques being used to analyze cell-free DNA in the maternal circulation for the prenatal detection of chromosome abnormalities and the evidence in support of each."
  • Noninvasive whole-genome sequencing of a human fetus[2] "Analysis of cell-free fetal DNA in maternal plasma holds promise for the development of noninvasive prenatal genetic diagnostics. Previous studies have been restricted to detection of fetal trisomies, to specific paternally inherited mutations, or to genotyping common polymorphisms using material obtained invasively, for example, through chorionic villus sampling. Here, we combine genome sequencing of two parents, genome-wide maternal haplotyping, and deep sequencing of maternal plasma DNA to noninvasively determine the genome sequence of a human fetus at 18.5 weeks of gestation. "
  • A noninvasive test to determine paternity in pregnancy[3] "Our approach shows that noninvasive prenatal paternity testing can be performed within the first trimester with the use of a maternal blood sample."
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<pubmed limit=5>Non-Invasive Prenatal Testing</pubmed>

Inheritance Genetics

Pedigree chart


Links: Genetic risk maternal age | Trisomy 21

Australia

A recent publication from NHMRC Medical Genetic Testing: information for health professionals (2010). This paper covers background information on all types of genetic tests, not just those associated with prenatal diagnosis.

Types of genetic tests

  • Somatic cell genetic testing involves testing tissue (usually cancer) for non-heritable mutations. This may be for diagnostic purposes, or to assist in selecting treatment for a known cancer.
  • Diagnostic testing for heritable mutations involves testing an affected person to identify the underlying mutation(s) responsible for the disease. This typically involves testing one or more genes for a heritable mutation.
  • Predictive testing for heritable mutations involves testing an unaffected person for a germline mutation identified in genetic relatives. The risk of disease will vary according to the gene, the mutation and the family history.
  • Carrier testing for heritable mutations involves testing for the presence of a mutation that does not place the person at increased risk of developing the disease, but does increase the risk of having an affected child developing the disease.
  • Pharmacogenetic testing for a genetic variant that alters the way a drug is metabolised. These variants can involve somatic cells or germline changes. Even if these variants are heritable (that is germline changes), the tests are usually of relevance to genetic relatives only if they are being treated with the same type of medication.


Links: NHMRC - Medical Genetic Testing: information for health professionals

USA

A new site developed by NIH "GeneTests" provides medical genetics information resources available at no cost to all interested persons. It contains educational information, a directory of genetic testing laboratories and links to other databases such as OMIM.


Links: GeneTests | Medline Plus - Genetic Testing


Ethics of Testing

Major developmental abnormalities detected early enough can be resolved far more easily than those discovered late in a pregnancy.

What are the ethical questions that are raised by prenatal testing? Future individual rights or parents rights? But what about diseases, like Huntington's, where a diagnostic test can be made but there are no current treatments for the postnatal (95% of cases adult onset) disease?

Huntington's disease

Guidelines for the molecular genetics predictive test

Recommendation 2.1 "the test is available only to individuals who have reached the age of majority."
Recommendation 7.2 "the couple requesting antenatal testing must be clearly informed that if they intend to complete the pregnancy if the fetus is a carrier of the gene defect, there is no valid reason for performing the test."

(excerpt from: IHA and the World Federation of Neurology Research Group on Huntington's Chorea. Guidelines for the molecular genetics predictive test in Huntington's disease.)

References

  1. <pubmed>24466384</pubmed>
  2. <pubmed>22674554</pubmed>
  3. <pubmed>22551147</pubmed>


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Prenatal Diagnosis Terms

  • blastomere biopsy - An ART preimplantation genetic diagnosis technique carried out at cleavage stage (day 3), excluding poor quality embryos, detects chromosomal abnormalities of both maternal and paternal origin. May not detect cellular mosaicism in the embryo.
  • blastocyst biopsy - An ART preimplantation genetic diagnosis technique carried out at blastocyst stage (day 4-5), removes several trophoblast (trophoderm) cells, detects chromosomal abnormalities of both maternal and paternal origin and may detect cellular mosaicism.
  • cell-free fetal deoxyribonucleic acid - (cffDNA) refers to fetal DNA circulating and isolated from the plasma portion of maternal blood.
  • false negative rate - The proportion of pregnancies that will test negative given that the congenital anomaly is present.
  • false positive rate - The proportion of pregnancies that will test positive given that the congenital anomaly is absent.
  • free β human chorionic gonadotrophin - beta-hCG subunit of hCG used as a diagnostic marker for: early detection of pregnancy, Trisomy 21, spontaneous abortion, ectopic pregnancy, hydatidiform mole or choriocarcinoma.
  • multiples of the median - (MoM) A multiple of the median is a measure of how far an individual test result deviates from the median and is used to report the results of medical screening tests, particularly where the results of the individual tests are highly variable.
  • negative predictive value - The probability that a congenital anomaly is absent given that the prenatal screening test is negative.
  • Non-Invasive Prenatal Testing - (NIPT) could refer to ultrasound or other imaging techniques, but more frequently used to describe analysis of cell-free fetal DNA circulating in maternal blood.
  • polar body biopsy - (PB biopsy) An ART preimplantation genetic diagnosis technique that removes either the first or second polar body from the zygote. As these are generated by oocyte meiosis they detects chromosomal abnormalities only on the female genetics.
  • positive predictive value - The probability that a congenital anomaly is present given that the prenatal screening test is positive.
  • pre-implantation genetic diagnosis - (PGD, pre-implantation genetic screening) a diagnostic procedure for embryos produced through Assisted Reproductive Technology (ART, in vitro fertilisation, IVF) for genetic diseases that would generate developmental abnormalities or serious postnatal diseases.
  • prenatal screening sensitivity - (detection rate) The probability of testing positive on a prenatal screening test if the congenital anomaly is present.
  • prenatal screening specificity - The probability of testing negative on a prenatal screening test if the congenital anomaly is absent.
  • single nucleotide polymorphisms - (SNPs) the variation in a single DNA nucleotide that occurs at a specific position in the genome.
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Cite this page: Hill, M.A. (2019, October 14) Embryology Non-Invasive Prenatal Testing. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Non-Invasive_Prenatal_Testing

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G