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Genetic Screening and Testing

Introduction

Every expectant mother wants to be sure that her baby is healthy, well-developed, and complications do not threaten the pregnancy. Modern technologies allow detecting pathologies at an early stage of pregnancy, which makes it possible to make the necessary decisions promptly. Genetic screening (prenatal screening) is a maternally and fetal-safe screening that can accurately identify the threat of genetic diseases and the risks of pregnancy complications. For parents it is highly important to ensure health safety for them and their children so that early diagnosis should regard as a preventive tool, which assists both parents and clinicians to secure fetus health.

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Concept Definition

The provided descriptive report explains how genetic screening and testing assists clinicians in determining cognitive disabilities in babies. This technique is more known as a prenatal test, which is highly essential for pregnant women. Genetic screening (prenatal screening) is a complex of diagnostic studies in the production of anomalies, which is developed and identified (brand management) of the pathology of the fetus. Genetic screening uses UZD screening (11-13 weeks, 16-18 weeks, 21-22 weeks, 30-32 weeks required number) and biochemical screening (consecutive test 13-13 weeks, and triple 16-18 weeks life) (DeThorne and Ceman 61). The double test is a personal association with the duration of plasma protein A-PAPP, chorionic gonadotropin. The triple test determines alpha-fetoprotein, chorionic gonadotropin, unbound estriol. Genetic screening is recommended for all long-term manufacturers of large manufacturers.

Besides, pregnancy screening reveals the possibility of chromosomal abnormalities or congenital disabilities in a future baby. Prenatal testing is performed to eliminate the likelihood of syndromes, like Down, Edwards, Patau, neural tube defects, and other anomalies of the placenta. It should be noted that the most common chromosomal abnormality is Down syndrome.

Such screening is based on the difference between indicators in the blood of a pregnant with chromosomal abnormalities and the blood properties of women who carry a healthy baby. The saturation of the markers is determined by the duration of pregnancy and the condition of the fetus (Shaffer et al. 502). Consequently, screening is assigned at a fixed interval when the risks are assessed as accurately as possible. Mostly, two such studies are required: the first and second trimesters, a double and a triple test, respectively.

Concept Description

Genetic screening is recommended for pregnant women who fall into the following categories:

  1. Age over 35;
  2. Ultrasound of the fetus showed deviation from the norms of development;
  3. One parent is a carrier of the genetic disease;
  4. The family already has a child or close relative with a chromosomal disease or congenital disability;
  5. Not yet aware of the pregnancy, the woman took potent drugs that were not recommended for use by pregnant women, did x-rays or were exposed to any radiation, were in stressful conditions for the body;
  6. Partners have related relationships (e.g., cousin and sister);
  7. The family wants to exclude the possibility of having a baby with developmental disorders or chromosomal diseases.

The genetic test allows clinicians to determine and identify these specific deviations in DNA:

  1. Trisomy (21 pairs of chromosomes (Down syndrome);
  2. The risk of trisomy on the 13th chromosome (Patau syndrome);
  3. Trisomy on the 18th pair of chromosomes (Edwards syndrome);
  4. Cornelia de Lange Syndrome;
  5. Smith-Lemley-Opitz syndrome;
  6. Shereshevsky-Turner syndrome;
  7. Triploidy of maternal origin;
  8. Nerve tube defects (anencephaly, spina bifida);
  9. Omphalocele (umbilical cord hernia).

It should be noted that most of these diseases have a significant impact on the quality of life of both the child and the whole family. Some of them can be corrected, for example, spina bifida in the mildest forms may not require treatment at all; some defects can be eliminated surgically, but several cases, even after surgery, will have negative consequences (Shaffer et al. 503). It is a mistake to think that chromosomal abnormalities are rare cases that number in the tens of thousands of newborns. Some anomalies are indeed infrequent, but Down syndrome occurs in a single case in 600-800 births. At the same time, even families who are not at any risk can lose in the genetic lottery.

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Genetic Screening Technique

Prenatal screening is performed twice – in the first and second trimesters of pregnancy. As noted earlier, in addition to assessing the risks of genetic pathologies, it allows clinicians to predict possible complications in pregnancy, such as late toxicosis, placental insufficiency, intrauterine hypoxia, preterm delivery. The first trimester, 11-13 weeks of pregnancy, should be screened, as the part of initial genetic screening. At this time, the activity of the embryo is still low, but the work of the placenta is already very active, so much information is provided by its indicators – free HCG (human chorionic gonadotropin) and PAPP-A (pregnancy-related plasma protein A) (DeThorne and Ceman 65). An indicator that does not meet the deadline determines a delay in intrauterine development or signal the risk of hypertensive conditions.

The first screening is combined with an ultrasound examination to assess compliance of fetal development with the standards. Pregnancy trimester one screening should be 11 to 13 weeks. Nonetheless, clinicians suggest that it is preferably 12 weeks, as one of the most appropriate time for reliable results. It detects the likelihood of pathologies, such as defect of the anterior abdominal wall, nerve tube, specific genetic pathological changes. Besides, the “double test” indicates the threat of abortion, fetoplacental insufficiency. The conclusion of the trimester one screening is based on ultrasound and biochemical blood analysis. Free β-HCG and PAPP-A are also calculated. At 10-12 weeks of pregnancy, the HCG level reaches its highest level and then decreases. The PAPP-A study should be performed at week 12 (Franceschini et al. 573). After 14 weeks, it is not informative. It is also necessary to measure the nasal bones, blood flow in the venous duct, to exclude regurgitation on the tricuspid valve. Trimester one biochemical screening gives a 90% chance of detecting Down Syndrome in combination with ultrasound markers. If necessary, it is recommended to calculate the individual risk of having a baby with chromosomal abnormalities.

The second prenatal screening is conducted from 14 to 20 weeks, preferably in 16-18 weeks, since many pathologies can be formed during this period. It is current for weeks 16-20 (preferably 17-18). Screening of the second trimester consists of a detailed ultrasound, biochemical analysis of blood from a vein (HCG, AFP, and EC), so to speak, “triple test.” Ultrasound examination in the second trimester confirms the development and determines the size of the fetus, eliminates anomalies of development of major organs and systems, evaluates amniotic fluid, length of the nasal bone, thigh and shoulder bones. The estimation of the increase or fall in hCG is registered, as in the first trimester. AFP is most informative at 17-18 weeks (Légaré et al.). The level of free estriol (E3) demonstrates the functioning of the fetoplacental system. Its fall of more than 40% indicates a threat of miscarriage. A complex combination of indicators is estimated – placental HCG, fetal AFP (alpha-fetoprotein), and free estriol, which characterize the state of the placenta, fetus, and the body of a woman. The second screening provides detailed information on the operation of the fetoplacental complex.

Not only does screening reveal the risk of chromosomal abnormalities in a baby, but it can also diagnose and prescribe appropriate therapy for various pregnancy complications. Screening conclusions are provided as a report with test data and generally accepted medical standards. The results provide indicators of the probable risk of trisomy in the form of a ratio of -1: 14000; therefore, 1 case for 14000 or more pregnancies (Shaffer et al. 505). Given all the data, their definition and interpretation, the gynecologist recommends to the woman additional consultation with the geneticist and undergo an advanced independent analysis.

Conclusion

Prevention of complications identified through screening helps prevent many complications of the last trimester of pregnancy and possibly save the life and health of the baby. It is important to remember that a risk group is not a diagnosis. Pregnant women who have been excluded from screening at the risk of pathologies do not require further studies. However, at her discretion, the woman decides to have her screenings or not. The most accurate method of diagnosis of chromosomal pathology is the analysis of fetal chromosomes, which gives an accurate diagnosis. To confirm (or refute), additional tests are needed – amniocentesis or chorionic villus biopsy.

Works Cited

DeThorne, Laura S., and Stephanie Ceman. “Genetic Testing and Autism: Tutorial for Communication Sciences and Disorders”. Journal of Communication Disorders, vol 74, 2018, pp. 61-73. Elsevier BV.

Franceschini, Nora et al. “Genetic Testing in Clinical Settings”. American Journal of Kidney Diseases, vol 72, no. 4, 2018, pp. 569-581. Elsevier BV.

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Légaré, France et al. “Improving Decision Making About Genetic Testing in The Clinic: An Overview of Effective Knowledge Translation Interventions”. PLOS ONE, vol 11, no. 3, 2016, p. e0150123. Public Library of Science (Plos).

Shaffer, Lisa G. et al. “Quality Assurance Checklist and Additional Considerations for Canine Clinical Genetic Testing Laboratories: A Follow-Up to The Published Standards and Guidelines”. Human Genetics, vol 138, no. 5, 2019, pp. 501-508. Springer Science and Business Media LLC.

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