Preimplantation Genetic Diagnosis

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Introduction

Human Embryo (day 3)
Human Embryo (day 5)

This current page is a general starting point for the topic of Preimplantation Genetic Screening (PGS) also called Preimplantation Genetic Diagnosis (PGD) began during the 1990's as an alternative to other forms of prenatal diagnosis.


"In the general population trisomies and sex chromosome aneuploidies account for approximately 70% of anomalies recognizable by conventional genetic analysis."[1]


Recently with the growth in Assisted Reproductive Technology (ART) or commonly known as In Vitro Fertilization (IVF), there is now a new form of prenatal diagnosis that involves genetic testing of the blastocyst before implantation. (More? Assisted Reproductive Technology)


Generally, in vitro fertilised embryos are first cultured for up to three days. By this time the conceptus is composed of 6 to 10 cells (blastomeres) from which 1 or 2 cells are then removed by a laser for genetic testing. Some studies have also removed cells, or the polar body, at earlier days following fertilisation. While other studies have collected cells from later stage (day 5) blastocyst either the trophectoderm (trophoblast) or inner cell mass (embryoblast).


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

Some Recent Findings

  • Euploidy in relation to blastocyst sex and morphology[2] "This is a retrospective cohort study at an academic medical center of patients who underwent in vitro fertilization with preimplantation genetic screening (PGS) from 2010 to 2015. Embryos were screened with 24-chromosome preimplantation genetic screening with day 5/6 trophectoderm biopsy. We investigated embryo euploidy in relation to morphology (expansion, inner cell mass, trophectoderm), embryo sex, biopsy day, and blastocyst cohort size. We used multivariate logistic regression to calculate odds ratios of euploidy in relation to these parameters. RESULTS: A total of 1559 embryos from 316 cycles and 233 patients (mean maternal age = 37.8 ± 4.2 years) were included in the analysis. Six hundred and twenty-eight blastocysts (40.3%) were found to be euploid. Expansion (p < 0.001), inner cell mass (ICM) (p < 0.01), and trophectoderm grade (p < 0.001) were significantly associated with embryo ploidy in bivariate models controlling for maternal age, while embryo sex, biopsy day, and blastocyst cohort size were not associated with embryo ploidy. In a multivariate model, we found that maternal age (p < 0.001), higher grade of expansion (p < 0.01), and better quality trophectoderm (p < 0.001 for A compared to C grade) remained significantly associated with increased embryo euploidy, but ICM grade was no longer significant. Embryo sex was not associated with ploidy status, though male embryos were found to be associated with higher trophectoderm scores (p < 0.02). CONCLUSIONS: This is the largest study to date to investigate PGS-tested embryo sex and ploidy status. While maternal age and some morphological parameters (expansion, trophectoderm grade) are associated with euploidy in our cohort, other parameters such as embryo sex, biopsy day, and cohort size are not. Though embryo sex was not associated with euploidy, male embryos were found to be associated with higher trophectoderm grades. Additional investigation in larger studies is warranted."
  • Review - patient decision-making factors and attitudes regarding preimplantation genetic diagnosis[3] "The increasing technical complexity and evolving options for repro-genetic testing have direct implications for information processing and decision making, yet the research among patients considering preimplantation genetic diagnosis (PGD) is narrowly focused. This review synthesizes the literature regarding patient PGD decision-making factors, and illuminates gaps for future research and clinical translation. Twenty-five articles met the inclusion criteria for evaluating experiences and attitudes of patients directly involved in PGD as an intervention or considering using PGD. Thirteen reports were focused exclusively on a specific disease or condition. Five themes emerged: (1) patients motivated by prospects of a healthy, genetic-variant-free child, (2) PGD requires a commitment of time, money, energy and emotions, (3) patients concerned about logistics and ethics of discarding embryos, (4) some patients feel sense of responsibility to use available technologies, and (5) PGD decisions are complex for individuals and couples. Patient research on PGD decision-making processes has very infrequently used validated instruments, and the data collected through both quantitative and qualitative designs have been inconsistent."
  • Preimplantation genetic diagnosis as a strategy to prevent having a child born with an heritable eye disease[4] "In developed countries, genetically inherited eye diseases are responsible for a high percentage of childhood visual impairment. We aim to report our experience using preimplantation genetic diagnostics (PGD) in order to avoid transmitting a genetic form of eye disease associated with childhood visual impairment and ocular cancer. MATERIAL AND METHODS: Retrospective case series of women who underwent in vitro fertilization (IVF) and PGD due to a familial history of inherited eye disease and/or ocular cancer, in order to avoid having a child affected with the known familial disease. Each family underwent genetic testing in order to identify the underlying disease-causing mutation. IVF and PGD treatment were performed; unaffected embryos were implanted in their respective mothers. RESULTS: Thirty-five unrelated mothers underwent PGD, and the following hereditary conditions were identified in their families: albinism (10 families); retinitis pigmentosa (7 families); retinoblastoma (4 families); blue cone monochromatism, achromatopsia, and aniridia (2 families each); and Hermansky-Pudlak syndrome, Leber congenital amaurosis, Norrie disease, papillorenal syndrome, primary congenital cataract, congenital glaucoma, Usher syndrome type 1F, and microphthalmia with coloboma (1 family each). Following a total of 88 PGD cycles, 18 healthy (i.e., unaffected) children were born." vision
  • The first successful application of preimplantation genetic diagnosis for hearing loss in Iran[5] "Hearing impairment (HI) caused by mutations in the connexin-26 gene (GJB2) accounts for the majority of cases with inherited, nonsyndromic sensorineural hearing loss. Due to the illegality of the abortion of deaf fetuses in Islamic countries, preimplantation genetic diagnosis (PGD) is a possible solution for afflicted families to have a healthy offspring. This study describes the first use of PGD for GJB2 associated non-syndromic deafness in Iran. GJB2 donor splicing site IVS1+1G>A mutation analysis was performed using Sanger sequencing for a total of 71 Iranian families with at least 1 deaf child diagnosed with non-syndromic deafness. In Vitro Fertilization (IVF) was performed, followed by PGD for a cousin couple with a 50% chance of having an affected child. Bi-allelic pathogenic mutations were found in a total of 12 families (~17 %); of which a couple was a PGD volunteer. The deaf woman in this family was homozygous and her husband was a carrier of the IVS1+1G>A gene mutation. Among 8 biopsied embryos, two healthy embryos were implanted which resulted in a single pregnancy and subsequent birth of a healthy baby boy. This is the first report of a successful application of PGD for hearing loss in Iran." hearing
More recent papers  
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Search term: Preimplantation Genetic Diagnosis

Wen-Bin He, Wen-Juan Xiao, Yue-Qiu Tan, Xiao-Meng Zhao, Wen Li, Qian-Jun Zhang, Chang-Gao Zhong, Xiu-Rong Li, Liang Hu, Guang-Xiu Lu, Ge Lin, Juan Du Novel mutations of PKD genes in Chinese patients suffering from autosomal dominant polycystic kidney disease and seeking assisted reproduction. BMC Med. Genet.: 2018, 19(1);186 PubMed 30333007

Javier Del Rey, Francisco Vidal, Lorena Ramírez, Nina Borràs, Irene Corrales, Iris Garcia, Olga Martinez-Pasarell, Silvia F Fernandez, Raquel Garcia-Cruz, Aïda Pujol, Alberto Plaja, Itziar Salaverria, Maria Oliver-Bonet, Jordi Benet, Joaquima Navarro Novel Double Factor PGT strategy analyzing blastocyst stage embryos in a single NGS procedure. PLoS ONE: 2018, 13(10);e0205692 PubMed 30332465

Antonio Capalbo, Valeria Romanelli, Cristina Patassini, Maurizio Poli, Laura Girardi, Adriano Giancani, Marta Stoppa, Danilo Cimadomo, Filippo Maria Ubaldi, Laura Rienzi Diagnostic efficacy of blastocoel fluid and spent media as sources of DNA for preimplantation genetic testing in standard clinical conditions. Fertil. Steril.: 2018, 110(5);870-879.e5 PubMed 30316433

Hassan Abolhassani, Fatemeh Kiaee, Marzieh Tavakol, Zahra Chavoshzadeh, Seyed Alireza Mahdaviani, Tooba Momen, Reza Yazdani, Gholamreza Azizi, Sima Habibi, Mohammad Gharagozlou, Masoud Movahedi, Amir Ali Hamidieh, Nasrin Behniafard, Mohammamd Nabavi, Mohammad Hassan Bemanian, Saba Arshi, Rasol Molatefi, Roya Sherkat, Afshin Shirkani, Reza Amin, Soheila Aleyasin, Reza Faridhosseini, Farahzad Jabbari-Azad, Iraj Mohammadzadeh, Javad Ghaffari, Alireza Shafiei, Arash Kalantari, Mahboubeh Mansouri, Mehrnaz Mesdaghi, Delara Babaie, Hamid Ahanchian, Maryam Khoshkhui, Habib Soheili, Mohammad Hossein Eslamian, Taher Cheraghi, Abbas Dabbaghzadeh, Mahmoud Tavassoli, Rasoul Nasiri Kalmarzi, Seyed Hamidreza Mortazavi, Sara Kashef, Hossein Esmaeilzadeh, Javad Tafaroji, Abbas Khalili, Fariborz Zandieh, Mahnaz Sadeghi-Shabestari, Sepideh Darougar, Fatemeh Behmanesh, Hedayat Akbari, Mohammadreza Zandkarimi, Farhad Abolnezhadian, Abbas Fayezi, Mojgan Moghtaderi, Akefeh Ahmadiafshar, Behzad Shakerian, Vahid Sajedi, Behrang Taghvaei, Mojgan Safari, Marzieh Heidarzadeh, Babak Ghalebaghi, Seyed Mohammad Fathi, Behzad Darabi, Saeed Bazregari, Nasrin Bazargan, Morteza Fallahpour, Alireza Khayatzadeh, Naser Javahertrash, Bahram Bashardoust, Mohammadali Zamani, Azam Mohsenzadeh, Sarehsadat Ebrahimi, Samin Sharafian, Ahmad Vosughimotlagh, Mitra Tafakoridelbari, Maziar Rahimi, Parisa Ashournia, Anahita Razaghian, Arezou Rezaei, Setareh Mamishi, Nima Parvaneh, Nima Rezaei, Lennart Hammarström, Asghar Aghamohammadi Fourth Update on the Iranian National Registry of Primary Immunodeficiencies: Integration of Molecular Diagnosis. J. Clin. Immunol.: 2018; PubMed 30302726

Older papers  
  • Review - Genetic Analysis of Human Preimplantation Embryos[6] "Preimplantation development comprises the initial stages of mammalian development, before the embryo implants into the mother's uterus. In normal conditions, after fertilization the embryo grows until reaching blastocyst stage. The blastocyst grows as the cells divide and the cavity expands, until it arrives at the uterus, where it "hatches" from the zona pellucida to implant into the uterine wall. Nevertheless, embryo quality and viability can be affected by chromosomal abnormalities, most of which occur during gametogenesis and early embryo development; human embryos produced in vitro are especially vulnerable. Therefore, the selection of chromosomally normal embryos for transfer in assisted reproduction can improve outcomes in poor-prognosis patients. Additionally, in couples with an inherited disorder, early diagnosis could prevent pregnancy with an affected child and would, thereby, avoid the therapeutic interruption of pregnancy. These concerns have prompted advancements in the use of preimplantation genetic diagnosis (PGD). Genetic testing is applied in two different scenarios: in couples with an inherited genetic disorder or carriers of a structural chromosomal abnormality, it is termed PGD; in infertile couples with increased risk of generating embryos with de novo chromosome abnormalities, it is termed preimplantation genetic screening, or PGS."
  • Preimplantation genetic screening (PGS) still in search of a clinical application: a systematic review[7] "Only a few years ago the American Society of Assisted Reproductive Medicine (ASRM), the European Society for Human Reproduction and Embryology (ESHRE) and the British Fertility Society declared preimplantation genetic screening (PGS#1) ineffective in improving in vitro fertilization (IVF) pregnancy rates and in reducing miscarriage rates. A presumably upgraded form of the procedure (PGS#2) has recently been reintroduced, and is here assessed in a systematic review. PGS#2 in comparison to PGS#1 is characterized by: (i) trophectoderm biopsy on day 5/6 embryos in place of day-3 embryo biopsy; and (ii) fluorescence in-situ hybridization (FISH) of limited chromosome numbers is replaced by techniques, allowing aneuploidy assessments of all 24 chromosome pairs. Reviewing the literature, we were unable to identify properly conducted prospective clinical trials in which IVF outcomes were assessed based on "intent to treat"."
  • Origins and rates of aneuploidy in human blastomeres[8] "The rate of maternal meiotic trisomy rose significantly with age, whereas other types of trisomy showed no correlation with age. Trisomies were mostly maternal in origin, whereas paternal and maternal monosomies were roughly equal in frequency. No examples of paternal meiotic trisomy were observed. Segmental error rates were found to be independent of maternal age."
  • Preimplantation genetic diagnosis for inherited breast cancer: first clinical application and live birth in Spain[9] "Carriers of a mutation in BRCA1/2 genes confront a high lifetime risk of breast and ovarian cancer and fifty percent probability of passing the mutation to their offspring. ...A 28-year-old BRCA1 mutation carrier (5273G>A in exon 19) with a strong maternal history of breast cancer and 2 years of infertility decided to pursue PGD to have a healthy descendent after an accurate assessment of her reproductive options. The procedure was approved by the national regulation authority and a PGD cycle was initiated. Four out of 6 embryos harbored the mutation. The two unaffected embryos were implanted in the uterus. A singleton pregnancy was achieved and a male baby was delivered at term. Consented umbilical cord blood testing confirmed the accuracy of the technique. Individualized PGD for inherited breast predisposition is feasible in the context of a multidisciplinary team."
  • Preimplantation genetic diagnosis (PGD) for Huntington's disease: the experience of three European centres[10] "This study provides an overview of 13 years of experience of preimplantation genetic diagnosis (PGD) for Huntington's disease (HD) at three European PGD centres in Brussels, Maastricht and Strasbourg. ... PGD workup was based on two approaches: (1) direct testing of the CAG-triplet repeat and (2) linkage analysis using intragenic or flanking microsatellite markers of the HTT gene. In total, 257 couples had started workup and 174 couples (70% direct testing, 30% exclusion testing) completed at least one PGD cycle. In total, 389 cycles continued to oocyte retrieval (OR). The delivery rates per OR were 19.8%, and per embryo transfer 24.8%, resulting in 77 deliveries and the birth of 90 children. We conclude that PGD is a valuable and safe reproductive option for HD carriers and couples at risk of transmitting HD."

Genetic Testing

Trisomy

Trisomy 21 karyotype cartoon

There are clinically more and more tests becoming available as we learn more about the genetic basis of some diseases. The most common diagnostic test relates to the current trend in an increasing maternal age, which has long been associated with an increase in genetic abnormalities, the most frequent of these is trisomy 21 or Down syndrome.

Links: Genetic risk maternal age | Trisomy 21

Single Gene Disorders

  • Cystic fibrosis
  • beta-thalassaemia
  • Spinal muscular atrophy
  • Sickle-cell anaemia
  • Huntington disease
  • Myotonic dystrophy type 1
  • Duchenne or Becker muscular dystrophy
  • Haemophilia
  • Fragile-X syndrome

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

Genetic Inheritance

The figures below show the pattern of inheritance of a range of genetic disorders. In addition to these patterns are the known effects of increased maternal age and the effects of genetic mutations in the embryo and newborn.

Inheritance Pattern images: Autosomal dominant inheritance | Autosomal recessive inheritance | X-Linked dominant (affected father) | X-Linked dominant (affected mother) | X-Linked recessive (affected father) | X-Linked recessive (carrier mother) | Mitochondrial genome inheritance | Codominant inheritance | Genogram symbols | Genetics

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. Kozlowski P, Burkhardt T, Gembruch U, Gonser M, Kähler C, Kagan KO, von Kaisenberg C, Klaritsch P, Merz E, Steiner H, Tercanli S, Vetter K & Schramm T. (2018). DEGUM, ÖGUM, SGUM and FMF Germany Recommendations for the Implementation of First-Trimester Screening, Detailed Ultrasound, Cell-Free DNA Screening and Diagnostic Procedures. Ultraschall Med , , . PMID: 30001568 DOI.
  2. Wang A, Kort J, Behr B & Westphal LM. (2018). Euploidy in relation to blastocyst sex and morphology. J. Assist. Reprod. Genet. , , . PMID: 30030712 DOI.
  3. Genoff Garzon MC, Rubin LR, Lobel M, Stelling J & Pastore LM. (2018). Review of patient decision-making factors and attitudes regarding preimplantation genetic diagnosis. Clin. Genet. , 94, 22-42. PMID: 29120067 DOI.
  4. Yahalom C, Macarov M, Lazer-Derbeko G, Altarescu G, Imbar T, Hyman JH, Eldar-Geva T & Blumenfeld A. (2018). Preimplantation genetic diagnosis as a strategy to prevent having a child born with an heritable eye disease. Ophthalmic Genet. , 39, 450-456. PMID: 29781739 DOI.
  5. Karimi Yazdi A, Davoudi-Dehaghani E, Rabbani Anari M, Fouladi P, Ebrahimi E, Sabeghi S, Eftekharian A, Fatemi KS, Emami H, Sharifi Z, Ramezanzadeh F, Tajdini A, Zeinali S & Amanpour S. (2018). The first successful application of preimplantation genetic diagnosis for hearing loss in Iran. Cell. Mol. Biol. (Noisy-le-grand) , 64, 1718. PMID: 30030956
  6. Garcia-Herrero S, Cervero A, Mateu E, Mir P, Póo ME, Rodrigo L, Vera M & Rubio C. (2016). Genetic Analysis of Human Preimplantation Embryos. Curr. Top. Dev. Biol. , 120, 421-47. PMID: 27475859 DOI.
  7. Gleicher N, Kushnir VA & Barad DH. (2014). Preimplantation genetic screening (PGS) still in search of a clinical application: a systematic review. Reprod. Biol. Endocrinol. , 12, 22. PMID: 24628895 DOI.
  8. Rabinowitz M, Ryan A, Gemelos G, Hill M, Baner J, Cinnioglu C, Banjevic M, Potter D, Petrov DA & Demko Z. (2012). Origins and rates of aneuploidy in human blastomeres. Fertil. Steril. , 97, 395-401. PMID: 22195772 DOI.
  9. Ramón Y Cajal T, Polo A, Martínez O, Giménez C, Arjona C, Llort G, Bassas L, Viscasillas P & Calaf J. (2012). Preimplantation genetic diagnosis for inherited breast cancer: first clinical application and live birth in Spain. Fam. Cancer , 11, 175-9. PMID: 22179695 DOI.
  10. Van Rij MC, De Rademaeker M, Moutou C, Dreesen JC, De Rycke M, Liebaers I, Geraedts JP, De Die-Smulders CE & Viville S. (2012). Preimplantation genetic diagnosis (PGD) for Huntington's disease: the experience of three European centres. Eur. J. Hum. Genet. , 20, 368-75. PMID: 22071896 DOI.

Reviews

Bodurtha J & Strauss JF. (2012). Genomics and perinatal care. N. Engl. J. Med. , 366, 64-73. PMID: 22216843 DOI.

Ly KD, Agarwal A & Nagy ZP. (2011). Preimplantation genetic screening: does it help or hinder IVF treatment and what is the role of the embryo?. J. Assist. Reprod. Genet. , 28, 833-49. PMID: 21743973 DOI.

Articles

Theodosiou AA & Johnson MH. (2011). The politics of human embryo research and the motivation to achieve PGD. Reprod. Biomed. Online , 22, 457-71. PMID: 21397558 DOI.

Harton GL, De Rycke M, Fiorentino F, Moutou C, SenGupta S, Traeger-Synodinos J & Harper JC. (2011). ESHRE PGD consortium best practice guidelines for amplification-based PGD. Hum. Reprod. , 26, 33-40. PMID: 20966462 DOI.

Harton GL, Harper JC, Coonen E, Pehlivan T, Vesela K & Wilton L. (2011). ESHRE PGD consortium best practice guidelines for fluorescence in situ hybridization-based PGD. Hum. Reprod. , 26, 25-32. PMID: 20966461 DOI.

Harton G, Braude P, Lashwood A, Schmutzler A, Traeger-Synodinos J, Wilton L & Harper JC. (2011). ESHRE PGD consortium best practice guidelines for organization of a PGD centre for PGD/preimplantation genetic screening. Hum. Reprod. , 26, 14-24. PMID: 20966460 DOI.

Harton GL, Magli MC, Lundin K, Montag M, Lemmen J & Harper JC. (2011). ESHRE PGD Consortium/Embryology Special Interest Group--best practice guidelines for polar body and embryo biopsy for preimplantation genetic diagnosis/screening (PGD/PGS). Hum. Reprod. , 26, 41-6. PMID: 20966459 DOI.

Journals

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Search Pubmed: Preimplantation Genetic Screening | Preimplantation Genetic Diagnosis



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. (2018, October 21) Embryology Preimplantation Genetic Diagnosis. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Preimplantation_Genetic_Diagnosis

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© Dr Mark Hill 2018, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G