Prenatal Diagnosis

Embryology - 5 Dec 2023        Expand to Translate
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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

ART Preimplantation blastomere biopsy

This current page is a general starting point for the topic of prenatal diagnosis, the links below are to resources that give more specific information about some diagnostic techniques available at different stages of pregnancy. The two major classes of techniques are invasive and non-invasive testing and the results of these tests most commonly show normal development. When abnormal development is identified this can be due to genetic, environmental, unknown causes or a combination of these effects. (More? Abnormal Development)

A trend in developed countries of an increasing maternal age, long associated with increased genetic abnormalities, has emphasised the need for good diagnostic low risk tests that allow informed decisions early in a pregnancy. (More? Genetic) In contrast, in developing countries environmental effects such as infections and nutrition can impact upon embryonic and fetal development (More? Environmental | Nutrition)

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

A Combined First Trimester Screening test (cFTS) involves a maternal ultrasound scan and a blood test at 11-13+6 weeks pregnancy.

Non-Invasive Prenatal Testing (NIPT) include new techniques that analyzes cell-free fetal DNA circulating in maternal blood or from fetal cells in the cervical canal.

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.

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

chorionic villus sampling	amniocentesis	ultrasound

Some Recent Findings

Do fetal extravillous trophoblasts circulate in maternal blood postpartum? "Circulating fetal extravillous trophoblasts may offer a superior alternative to cell-free fetal DNA for noninvasive prenatal testing. Cells of fetal origin are a pure source of fetal genome, hence, unlike cell-free noninvasive prenatal test, fetal cell-based noninvasive prenatal test is not expected to be affected by maternal DNA. However, circulating fetal cells from previous pregnancies may lead to confounding results. ...Fetal extravillous trophoblasts were found in all the 10 samples from pregnant women in gestational age of 10-14 weeks. However, only four out of 11 blood samples taken from women, one to three days postpartum rendered fetal extravillous trophoblasts. And only two out of 11 samples rendered fetal extravillous trophoblasts at four weeks postpartum. In this preliminary dataset on few pregnancies, none of the samples rendered any fetal cells at or after eight weeks postpartum, showing that cell-based noninvasive prenatal testing based on fetal extravillous trophoblasts is unlikely to be influenced by circulating cells from previous pregnancies." Non-Invasive Prenatal Testing to detect chromosome aneuploidies in 57,204 pregnancies "Non-invasive prenatal testing (NIPT) has been widely used to detect common fetal chromosome aneuploidies, such as trisomy 13, 18, and 21 (T13, T18, and T21), and has expanded to sex chromosome aneuploidies (SCAs) during recent years, but few studies have reported NIPT detection of rare fetal chromosome aneuploidies (RCAs). In this study, we evaluated the clinical practical performance of NIPT to analyze all 24 chromosome aneuploidies among 57,204 pregnancies in the Suzhou area of China. METHODS: This was a retrospective analysis of prospectively collected NIPT data from two next-generation sequencing (NGS) platforms (Illumina and Proton) obtained from The Affiliated Suzhou Hospital of Nanjing Medical University. NIPT results were validated by karyotyping or clinical follow-up. RESULTS: NIPT using the Illumina platform identified 586 positive cases; fetal karyotyping and follow-up results validated 178 T21 cases, 49 T18 cases, 4 T13 cases, and 52 SCAs. On the Proton platform, 270 cases were positive during NIPT. Follow-up confirmed 85 T21 cases, 17 T18 cases, 4 T13 cases, 28 SCAs, and 1 fetal chromosome 22 aneuploidy case as true positives. There were 5 false-negative results, including 4 T21 and 1 T18 cases. The NGS platforms showed similar sensitivities and positive predictive values (PPVs) in detecting T21, T18, T13 and SCAs (p > 0.01). However, the Proton platform showed better specificity in detecting 45, X and the Illumina platform had better specificity in detecting T13 (p < 0.01). The major factor contributing to NIPT false-positives on the Illumina platform was false SCAs cases (65.11%). Maternal chromosome aneuploidies, maternal cancers, and confined placental mosaicism caused discordant results between fetal karyotyping and NIPT. CONCLUSION: NIPT with NGS showed good performance for detecting T13, T18, and T21. The Proton platform had better performance for detecting SCAs, but the NIPT accuracy rate for detecting RCAs was insufficient." Sensitivity of prenatal ultrasound for detection of Trisomy 18 "To evaluate the sensitivity of prenatal ultrasound (US) for trisomy (T18) diagnosis and describe US findings in a large tertiary care institution in the USA. Materials and methods: This was a retrospective cohort of all T18 cases diagnosed at our institution from October 2004 to October 2014 based on prenatal or postnatal genetic diagnostic testing. We included all women with a fetus affected by T18 who had a comprehensive US by a maternal-fetal medicine specialist performed at our institution. US findings were reviewed, classified by organ system, and categorized as an anomaly or soft marker. Chi-square or t-test was used for statistical analysis. Results: We included 128 cases of T18 with confirmed cytogenetic analysis -110 (86%) of which were diagnosed prenatally or suspected by cell-free DNA and confirmed postnatally, and 18 of which underwent neonatal blood sampling alone. One hundred and twenty-one (95%) had at least one abnormal US finding. Anomalies were more frequently identified on US at ≥20 weeks as compared with <20 weeks (93% versus 76%; p = .004). The mean number of findings detected per fetus was 5.1 ± 3.0. Fetuses diagnosed by postnatal sampling alone had a similar number of US exams performed and number of abnormal findings compared to those diagnosed prenatally. Conclusion: Ninety-five percent of fetuses with T18 had at least one abnormal US finding. This sensitivity of is higher than reported in most prior studies, but is not 100%, and should be considered when counseling women regarding prenatal diagnosis of T18. Rationale: Historical detection rates for abnormal sonographic findings in trisomy 18 fetuses range from 70% to 100%. These studies are limited by small sample sizes. This is a contemporary study of ultrasound findings in a large group of women with confirmed trisomy 18 by prenatal or postnatal genetic diagnosis. We provide expansive detail on soft markers and anomalies broken down by organ-system and gestational age." First trimester combined screening biochemistry in detection of congenital heart defects "To evaluate the performance of first trimester biochemical markers, pregnancy-associated plasma protein-A (PAPP-A), free beta human chorionic gonadotropin (fβ-hCG), and nuchal translucency (NT) in detection of severe congenital heart defects (CHDs). Methods: During the study period from 1 January 2008 to 31 December 2011, biochemical markers and NT were measured in 31,144 women as part of voluntary first trimester screening program for Down's syndrome in Northern Finland. Data for 71 severe CHD cases and 762 controls were obtained from the hospital records and from the National Medical Birth Register, which records the birth of all liveborn and stillborn infants, and from the National Register of Congenital Malformations that receives information about all the CHD cases diagnosed in Finland. Results: Both PAPP-A and fβ-hCG multiple of median (MoM) values were decreased in all severe CHDs: 0.71 and 0.69 in ventricular septal defects (VSDs), 0.58 and 0.88 in tetralogy of Fallot cases (TOFs), 0.82 and 0.89 in hypoplastic left heart syndromes (HLHSs), and 0.88 and 0.96 in multiple defects, respectively. NT was increased in all study groups except of VSD group. ROC AUC was 0.72 for VSD when combining prior risk with PAPP-A and fβ-hCG. Adding NT did not improve the detection rate. With normal NT but decreased (<0.5 MoM) PAPP-A and fβ-hCG odds ratios for VSD and HLHS were 19.5 and 25.6, respectively. Conclusions: Maternal serum biochemistry improves the detection of CHDs compared to NT measurement only. In cases with normal NT measurement but low concentrations of both PAPP-A and fβ-hCG, an alert for possible CHD, especially VSD, could be given with thorough examination of fetal heart in later ultrasound scans." cardiovascular abnormalities Noninvasive blood tests for fetal development predict gestational age and preterm birth "Noninvasive blood tests that provide information about fetal development and gestational age could potentially improve prenatal care. Ultrasound, the current gold standard, is not always affordable in low-resource settings and does not predict spontaneous preterm birth, a leading cause of infant death. In a pilot study of 31 healthy pregnant women, we found that measurement of nine cell-free RNA (cfRNA) transcripts in maternal blood predicted gestational age with comparable accuracy to ultrasound but at substantially lower cost. In a related study of 38 women (23 full-term and 15 preterm deliveries), all at elevated risk of delivering preterm, we identified seven cfRNA transcripts that accurately classified women who delivered preterm up to 2 months in advance of labor. These tests hold promise for prenatal care in both the developed and developing worlds, although they require validation in larger, blinded clinical trials." Cochrane Review - Genomics-based non-invasive prenatal testing for detection of fetal chromosomal aneuploidy in pregnant women Common fetal aneuploidies include Down syndrome (trisomy 21 or T21), Edward syndrome (trisomy 18 or T18), Patau syndrome (trisomy 13 or T13), Turner syndrome (45,X), Klinefelter syndrome (47,XXY), Triple X syndrome (47,XXX) and 47,XYY syndrome (47,XYY). Prenatal screening for fetal aneuploidies is standard care in many countries, but current biochemical and ultrasound tests have high false negative and false positive rates. The discovery of fetal circulating cell-free DNA (ccfDNA) in maternal blood offers the potential for genomics-based non-invasive prenatal testing (gNIPT) as a more accurate screening method. Two approaches used for gNIPT are massively parallel shotgun sequencing (MPSS) and targeted massively parallel sequencing (TMPS). ...These results show that MPSS and TMPS perform similarly in terms of clinical sensitivity and specificity for the detection of fetal T31, T18, T13 and sex chromosome aneuploidy (SCA). ...We conclude that given the current data on the performance of gNIPT, invasive fetal karyotyping is still the required diagnostic approach to confirm the presence of a chromosomal abnormality prior to making irreversible decisions relative to the pregnancy outcome. However, most of the gNIPT studies were prone to bias, especially in terms of the selection of participants."

More recent papers

This table allows an automated computer search of the external PubMed database using the listed "Search term" text link. This search now requires a manual link as the original PubMed extension has been disabled. The displayed list of references do not reflect any editorial selection of material based on content or relevance. References also appear on this list based upon the date of the actual page viewing. References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability. More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Prenatal Diagnosis | Non-Invasive Prenatal Testing

Older papers

These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table. See also the Discussion Page for other references listed by year and References on this current page. Fetal genome profiling at 5 weeks of gestation after noninvasive isolation of trophoblast cells from the endocervical canal "We have isolated intact trophoblast cells from Papanicolaou smears collected noninvasively at 5 to 19 weeks of gestation for next-generation sequencing of fetal DNA. ...The data revealed fetal DNA fractions of 85 to 99.9%, with 100% correct fetal haplotyping. This noninvasive platform has the potential to provide comprehensive fetal genomic profiling as early as 5 weeks of gestation." An Economic Analysis of Cell-Free DNA Non-Invasive Prenatal Testing in the US General Pregnancy Population "Analyze the economic value of replacing conventional fetal aneuploidy screening approaches with non-invasive prenatal testing (NIPT) in the general pregnancy population. METHODS: Using decision-analysis modeling, we compared conventional screening to NIPT with cell-free DNA (cfDNA) analysis in the annual US pregnancy population. Sensitivity and specificity for fetal aneuploidies, trisomy 21, trisomy 18, trisomy 13, and monosomy X, were estimated using published data and modeling of both first- and second trimester screening. Costs were assigned for each prenatal test component and for an affected birth. ...Based on our analysis, universal application of NIPT would increase fetal aneuploidy detection rates and can be economically justified. Offering this testing to all pregnant women is associated with substantial prenatal healthcare benefits." Increasing Live Birth Rate by Preimplantation Genetic Screening of Pooled Polar Bodies Using Array Comparative Genomic Hybridization "To overcome this disadvantage, we tested a strategy involving the pooling of DNA from both polar bodies before DNA amplification. We retrospectively studied 351 patients, of whom 111 underwent polar body array-CGH before embryo transfer. In the group receiving pooled polar body array-CGH (aCGH) analysis, 110 embryos were transferred, and 29 babies were born, corresponding to live birth rates of 26.4% per embryo and 35.7% per patient. In contrast, in the control group, the IVF treatment was performed without preimplantation genetic screening (PGS). For this group, 403 embryos were transferred, and 60 babies were born, resulting in live birth rates of 14.9% per embryo and 22.7% per patient. In conclusion, our data show that in the aCGH group, the use of aneuploidy screening resulted in a significantly higher live birth rate compared with the control group, supporting the benefit of PGS for IVF couples in addition to the suitability and effectiveness of our polar body pooling strategy." Noninvasive Prenatal Testing: The Future Is Now "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 "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 "Our approach shows that noninvasive prenatal paternity testing can be performed within the first trimester with the use of a maternal blood sample."

Maternal Blood Test

Maternal blood tests are usually offered in the first trimester.

• full blood count
• blood group and antibodies
• free b-hCG and PAPP-A
• glucose challenge - for diabetes
• random blood glucose
• sickle cell and Thalassaemia (Haemoglobinopathy) - for at risk women (Ethnic groups with high risk include: Mediterranean, Middle Eastern, African, Asian, Pacific Islander, South American, New Zealand Maori)
• Infections
  • syphilis
  • rubella
  • hepatitis B
  • hepatitis C
  • HIV antibodies

Other maternal tests:

• ultrasound - check dates, number of fetuses and development
• midstream urine - infections
• chlamydia screening

Amniocentesis

Amniocentesis is a prenatal diagnostic test carried out mainly between 14th to 18th week of pregnancy. Amniotic fluid is taken from the uterus, sent to a diagnostic laboratory and embryonic cells isolated from the amniotic fluid. No anaesthetic is required, and a result is usually obtained in about three to four weeks. When the test is carried out by an obstetrician experienced in the technique, the risk of a miscarriage related to the test is about 1 %. Links: Amniocentesis | Placenta - Amnionic Sac | Ultrasound

Chorionic Villus Sampling

Chorionic Villus Sampling (CVS) test is done in the 10th to 12th week after the first day of the mother's last menstrual period. The test is done by looking at cells taken from the chorionic membrane or placenta. No anaesthetic is required, and a test result is usually available in two to three weeks. When the test is carried out by an obstetrician experienced in the technique, the risk of miscarriage related to the test is about 2 %. (Modified from: Checking your baby's health before birth. State Health Publication Number (PA) 94-090) Potential disadvantages include maternal cell contamination, placental mosaicism and failure to obtain an adequate specimen. This may result in the need for a repeat procedure or amniocentesis. Links: Chorionic Villus Sampling | Placenta - Amnionic Sac | Ultrasound

Cordocentesis

Percutaneous umbilical blood sampling (PUBS, fetal blood sampling, umbilical vein sampling)

This chromosome analysis test is done at in the 18th week or later of high-risk pregnancies. The technique may be used when either alternative tests (amniocentesis, CVS, ultrasound) are either inconclusive or not achievable (severe oligohydramnios).

The risk of a miscarriage related to the test is about 3 per cent (occurring in 3 in 100 pregnancies).

Coelocentesis

This is a technique of sampling of extracoelomic fluid usually for an early prenatal diagnostic technique.

Fetal Fibronectin

As a prenatal diagnostic test, a positive fetal fibronectin test result can indicate a higher risk of preterm delivery, but may also has false positive results. The negative result is more reliable as an indicator of reduced risk of preterm birth.

(fFN) is an extracellular matrix glycoprotein produced by fetal cells. Fetal fibronectin appears to act as an adhesive between the interface of the chorion and the decidua (fetal membrane and uterine lining).

Non-Invasive Prenatal Testing

A published survey of clinicians from 28 countries worldwide reported that NIPT is available in their country (n=43) and that they offer NIPT in their current practice (n=38). Eighteen respondents from 14 countries reported that there are plans to introduce NIPT into routine antenatal care in their country. Test prices varied widely, ranging from $US 350 - $US 2900, and several respondents observed that high test prices limited or restricted widespread use of NIPT.

See also recent Non-Invasive Prenatal Testing (NIPT) articles in Australian Family Physician and JAMA (USA).

Cervical Canal Trophoblasts

Beginning in 2009, a diagnostic trial indicated that fetal cytotrophoblast cells could be collected by transcervical sampling for genetic analysis. A recent 2016 study has identified fetal genome profiling as early as gestation weeK 5 GA using this technique.

Links: Trophoblast

Genetic Testing

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.

Inheritance Genetics

Pedigree chart

• 

  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

Links: Genetic risk maternal age | Trisomy 21

Australia

Trisomy 21

• Department of Health 9.3 Screening tests in the first trimester combined test (nuchal translucency thickness, free beta-human chorionic gonadotrophin, pregnancy-associated plasma protein-A)
• NSW Health (2007) Prenatal Testing/Screening for Down Syndrome & Other Chromosomal Abnormalities PDF.

The Royal Hospital for Women (2014) Trisomy 21 Screening, Including Non-Invasive Prenatal Testing (Nipt) PDF

• Better Health Victoria trisomy disorders

A 2010 publication from NHMRC Medical Genetic Testing: information for health professionals 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

Comparative Genomic Hybridization

This new test under development is based upon microarray-based comparative genomic hybridization (array CGH).

All fetal cells should have complete copies of maternal and paternal genomes. The test compares regions of fetal DNA that deviate from this "pattern" due to either too much or too little DNA, alterations reflect regions of the genome that are either copied or deleted. These genetic changes may therefore cause disease.

Links: Comparative Genomic Hybridization

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

Journals

Prenatal Diagnosis communicates the results of clinical and basic research in prenatal and preimplantation diagnosis in humans, and animal and in vitro models,

http://www.ncbi.nlm.nih.gov/pubmed?term=%22Prenat+Diagn%22[jour]

Articles

Liston R, Sawchuck D & Young D. (2007). Fetal health surveillance: antepartum and intrapartum consensus guideline. J Obstet Gynaecol Can , 29, S3-56. PMID: 17845745

Search Pubmed

November 2010 "Prenatal Diagnosis" All (63715) Review (8631) Free Full Text (6349)

Search Pubmed: Prenatal Diagnosis

Prenatal Diagnosis Terms

• ART - Assisted Reproductive Technology a general term to describe all the clinical techniques used to aid fertility.

• 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 - (cfDNA) refers to fetal DNA circulating and isolated from the plasma portion of maternal blood. Can be performed from GA 10 weeks as a first-tier test or as a second-tier test, with women with increased probability on combined first trimester screening offered cfDNA or diagnostic testing.

• 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.

• quadruple test (maternal serum testing of a-fetoprotein Template:AFP, free B-hCG or total hCG, unconjugated estriol, and inhibin A) is a fetal chromosomal anomaly test usually carried out later in pregnancy (GA 14 to 20 weeks).

• single nucleotide polymorphisms - (SNPs) the variation in a single DNA nucleotide that occurs at a specific position in the genome.

• triple test - (maternal serum testing of a-fetoprotein Template:AFP, free B-hCG or total hCG, and unconjugated estriol) is a fetal chromosomal anomaly test usually carried out later in pregnancy (GA 14 to 20 weeks).

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

• Australian and New Zealand - College of Obstetricians and Gynaecologists Intrapartum Fetal Surveillance Clinical Guidelines - Second Edition (June 2011)
• Canada - Society of Obstetricians and Gynaecologists of Canada
  • Clinical Practice Guidelines
  • Fetal health Surveillance: antepartum and intrapartum Consensus Guideline PDF (Sept 2007)

• Mayo Clinic [www.mayoclinic.org/tests-procedures/noninvasive-prenatal-testing/basics/definition/prc-20012964 Noninvasive Prenatal Testing]

Glossary Links

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Cite this page: Hill, M.A. (2023, December 5) Embryology Prenatal Diagnosis. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Prenatal_Diagnosis

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© Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G