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Encyclopedia > Prenatal diagnosis

Prenatal diagnosis is the diagnosis of disease or condition in a fetus or embryo before it is born. The aim is to detect birth defects such as neural tube defects, chromosome abnormalities, genetic diseases and other conditions. It can also be used to determine the gender of the unborn baby. In general, a diagnosis (plural diagnoses) covers a broad spectrum, or spectra, of testing in some form of analysis; such tests based on some collective reasoning is called the method of diagnostics, leading then to the results of those tests by ideal (ethics) would then be considered a diagnosis, but... Human fetus at eight weeks. ... It has been suggested that embryology be merged into this article or section. ... A congenital disorder is a medical condition or defect that is present at or before birth (for example, congenital heart disease). ... The neural tube is the embryonal structure that gives rise to the brain and spinal cord. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... A genetic disorder, or genetic disease is a disease caused, at least in part, by the genes of the person with the disease. ...


Diagnostic prenatal testing is invasive (ie. amniocentesis, and chorionic villus sampling). non-invasive methods are called "screens". Non-invasive techniques can only evaluate risk of a condition and cannot determine 100% if the fetus has a condition. Non-invasive techniques include examinations of the mother's womb through ultrasonography and maternal serum screens (i.e. Alpha-fetoprotein) If an abnormality is indicated by a non-invasive procedure, a more invasive technique may be employed to gather more information. The term invasive in Medicine has two meanings: A medical procedure which penetrates or breaks the skin or a body cavity, i. ... Amniocentesis, or an Amniotic Fluid Test (AFT), is a medical procedure used for prenatal diagnosis, in which a small amount of amniotic fluid is extracted from the amnion around a developing fetus. ... Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine genetic abnormalities in the fetus. ... The term non-invasive in medicine has two meanings: A medical procedure which does not penetrate or break the skin or a body cavity, i. ... Medical ultrasonography is an ultrasound-based imaging diagnostic technique used to visualize internal organs, their size, structure and their pathological lesions. ... Alpha-fetoprotein (AFP) is a protein that is normally only produced in the foetus during its development. ...


Invasive techniques include amniocentesis, which can be done from about 14 weeks gestation, and usually up to about 20 weeks, and chorionic villus sampling which can be done earlier (between 9.5 and 12.5 weeks gestation) but which is slightly more risky to the unborn child. Amniocentesis, or an Amniotic Fluid Test (AFT), is a medical procedure used for prenatal diagnosis, in which a small amount of amniotic fluid is extracted from the amnion around a developing fetus. ... Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine genetic abnormalities in the fetus. ...

Contents

Reasons for prenatal diagnosis

Knowing a fetus is abnormal before birth allows parents to plan for any health needs of their baby in advance of it being born. It can also prepare them for the birth, enabling them to receive counselling before birth, reducing the shock and other reactions when the baby is born. In addition, it gives parents the option of abortion of the fetus.


Having this information in advance of the birth means that healthcare staff can better prepare for the delivery, and have suitable treatment ready for when the baby is born.


The type of prenatal diagnosis done depends on the situation of the parents. In an older mother (for instance over 35), or a parent with an inheritable genetic condition, an invasive technique may be selected because it is usually more accurate. These techniques can detect chromosome abnormalities (such as Down's syndrome) which are more common as a woman's age increases, or a specific genetic problem that might run in the family. Genetic counseling is often offered to help parents decide what type of testing is right for their situation. Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Genetic counseling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning in order to prevent, avoid or...


An estimated 50-70% of expectant parents would like to know the gender of their child ahead of delivering the baby [1], which can also be determined through prenatal testing.

Risk factors qualifying a woman for prenatal testing

  • Pregnant women over the age of 35
  • Women who have previously had premature babies or babies with a birth defect, especially heart or genetic problems
  • Women who have high blood pressure, lupus, diabetes, asthma, or epilepsy
  • Women whose partners have ethnic backgrounds prone to genetic disorders
  • Women who are pregnant with multiples (twins or more)

Arterial hypertension, or high blood pressure is a medical condition where the blood pressure is chronically elevated. ... Lupus is Latin for wolf. It may refer in various languages, including English, to: several diseases: Lupus anticoagulant, an antibody causing a delay in coagulation Lupus erythematosus, the autoimmune disease (also known as systemic lupus erythematosus, or SLE) Drug-induced lupus erythematosus, a drug-induced form of SLE Lupus nephritis... This article is about the disease that features high blood sugar. ...

Ethical and practical issues

Ethical issues of prenatal testing

  • The option to continue a pregnancy or abortion is the main choice after most prenatal testing.
  • Are the risks of prenatal diagnosis, such as amniocentesis worth the potential benefit?
  • Some fear that this may lead to being able to pick and choose what children parents would like to have. This could lead to choice in sex, physical characteristics, and personality in children.
  • Knowing about certain birth defects, such as spina bifida, before birth may give the option of fetal surgery during pregnancy, or to assure that the appropriate treatment and/or surgery be provided immediately after birth.
  • Are mentally or physically different children less valuable in our society?
  • How to ensure that information about testing options is given in a non-directive and supportive way.
  • That parents are well informed if they have to consider abortion vs. continuing a pregnancy. See wrongful abortion.

Amniocentesis, or an Amniotic Fluid Test (AFT), is a medical procedure used for prenatal diagnosis, in which a small amount of amniotic fluid is extracted from the amnion around a developing fetus. ... Open fetal surgery is an invasive form of fetal intervention in the treatment of birth defects where the uterus is opened up for direct surgery on the fetus. ... The term Wrongful Abortion was defined by Perry & Adar as an abortion that a pregnant woman is induced to undergo by negligent conduct (usually a medical misrepresentation). ...

Will the result of the test affect treatment of the fetus?

In some genetic conditions, for instance cystic fibrosis, an abnormality can only be detected if DNA is obtained from the baby. Usually an invasive method is needed to do this.


If a genetic disease is detected, there is often no treatment that can help the fetus until it is born. It does give parents the option to consider abortion of the baby.


If abortion isn't an option for a particular couple (because of their own beliefs), invasive prenatal diagnosis of such a condition is unhelpful as the test puts the child at risk, and knowing the result doesn't help the child. Genetic counseling can help families make informed decisions regarding results of prenatal diagnosis. Genetic counseling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning in order to prevent, avoid or...


False positives and false negatives

Ultrasound, which is considered a screening test, of an unborn baby can sometimes miss subtle abnormalities. For example studies show that a detailed ultrasound, also called a level 2 ultrasound, can detect about 80% of spina bifida. Ultrasound results may also show "soft signs," such an Echogenic intracardiac focus or Choroid plexus cyst, which are usually normal, but can be associated with an increased risk for chromosome abnormalities. Echogenic intracardiac focus (EIF) is a small bright spot seen in the baby’s heart on an ultrasound exam. ... The brain contains pockets or spaces called ventricles with a spongy layer of cells and blood vessels called the choroid plexus. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...


Other screening tests, such as the AFP triple test, can have false positives and false negatives. Even when the AFP triple test results are positive, usually the pregnancy is normal, but additional diagnostic tests may be offered. Both false positives and false negatives will have a large impact to a couple when they are told the result, or when the child is born. Diagnostic tests, such as amniocentesis, are considered to be very accurate for the defects they check for. The triple test, also called triple screen or the Barts test, is an investigation performed during pregnancy (usually the second trimester) for fetal trisomy 21 (Down syndrome). ... Type I errors (or α error, or false positive) and type II errors (β error, or a false negative) are two terms used to describe statistical errors. ... Type I errors (or α error, or false positive) and type II errors (β error, or a false negative) are two terms used to describe statistical errors. ... Diagnosis (from the Greek words dia = by and gnosis = knowledge) is the process of identifying a disease by its signs, symptoms and results of various diagnostic procedures. ...


No prenatal test can detect all forms of birth defects and abnormalities.


Societal Pressures on Prenatal Testing Decisions Amniocentesis has become the standard of care for prenatal care visits for women who are “at risk” or over a certain age. All obstetricians offer patients the AFP triple test, HIV test and ultrasounds routinely. However, almost all women meet with a genetic counselor before deciding whether to have prenatal diagnosis. It is the role of the genetic counselor to accurately inform women of the risks and benefits of prenatal diagnosis. Genetic counselors are trained to be non-directive and to support the patient's decision. Some doctors do advise women to have certain prenatal tests and patient's partner may also influence the woman's decision. The triple test, also called triple screen or the Barts test, is an investigation performed during pregnancy (usually the second trimester) for fetal trisomy 21 (Down syndrome). ... Species Human immunodeficiency virus 1 Human immunodeficiency virus 2 Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immunodeficiency syndrome (AIDS, a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections). ... Genetic counseling generally refers to prenatal counseling done when a genetic condition is suspected in a pregnancy. ...


Methods of prenatal diagnosis

Non-invasive methods:

  • Examination of the mother's uterus from outside the body. (i.e. Feeling the mother's 'stomach'.)
  • Ultrasound detection - Commonly dating scans (sometimes known as booking scans) from 7 weeks to confirm pregnancy dates and look for twins. Later morphology scans from 18 weeks may check for the baby's sex and any abnormal development. The specialised nuchal scan at 11-13 weeks may be used to identify higher risks of Downs syndrome.
  • Second trimester maternal serum screening (AFP screening, triple screen, or quad screen) can check levels of alpha fetoprotein, β-hCG, inhibin-A and estriol in the mother's serum.
  • First trimester maternal serum screening can check levels of free β-hCG and PAPP-A in the mother's serum, and combine these with the measurement of nuchal translucency (NT). Some institutions also look for the presence of a fetal nasalbone on the ultrasound.
  • Integrated, Sequential, and Contingent screening tests use serum samples from both first and second trimester, as well as the nuchal translucency measurement to calculate risks. With Integrated screening, a report is only produced after both samples have been analyzed. With Sequential screening, a first report is produced after the first trimester sample has been submitted, and a final report after the second sample. With Contingent screening, patients at very high or very low risks will get reports after the first trimester sample has been submitted. Only patients with moderate risk will be asked to submit a second trimester sample, after which they will receive a report combining information from both serum samples and the NT measurement.
  • Detection of fetal blood cells in maternal blood. With this technique it is technically possible to obtain a sample of the baby's DNA using blood cells from the fetus, that have made their way into the mother's bloodstream.

Invasive methods: The uterus or womb is the major female reproductive organ of most mammals, including humans. ... Medical ultrasonography is an ultrasound-based imaging diagnostic technique used to visualize internal organs, their size, structure and their pathological lesions. ... Fraternal twin boys bathing Identical Twin Girls Sleeping Twins in animal biology is a form of multiple birth in which the mother gives birth to two offspring from the same pregnancy, some of the same gender, others of opposite. ... Nuchal Scan is a prenatal screening ultrasound scan to help identify higher risks of a Downs syndrome affected fetus, particularly for older mothers who have higher risks of such pregnancies. ... Alpha-fetoprotein screening, also called AFP screening, triple test, and expanded AFP screening, is a screening blood test usually offered between 15-20 weeks of pregnancy. ... Alpha-fetoprotein (AFP) is a protein that is normally only produced in the fetus during its development. ... Human chorionic gonadotropin (hCG) is a peptide hormone produced in pregnancy, that is made by the embryo soon after conception and later by the syncytiotrophoblast (part of the placenta). ... Inhibin is a peptide that is an inhibitor of FSH synthesis and secretion and participates in the regulation of the menstrual cycle. ... Chemical structure of estriol Estriol (also oestriol) is one of the three main estrogens produced by the human body. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ... Human chorionic gonadotropin (hCG) is a peptide hormone produced in pregnancy, that is made by the embryo soon after conception and later by the syncytiotrophoblast (part of the placenta). ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ... Late in the first trimester, an echolucent area can be identified at the back of the neck of normal fetuses. ... Late in the first trimester, an echolucent area can be identified at the back of the neck of normal fetuses. ...

  • Chorionic villus sampling - Involves getting a sample of the chorionic villus and testing it. This can be done earlier than amniocentesis, but is a more risky procedure.
  • Amniocentesis - This can be done once enough amniotic fluid has developed to sample. Cells from the baby will be floating in this fluid, and can be separated and tested.
  • Embroscopy and fetoscopy - These involve putting a probe into a women's uterus to observe (with a video camera), or to sample blood or tissue from the baby.

Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine genetic abnormalities in the fetus. ... The chorion undergoes rapid proliferation and forms numerous processes, the chorionic villi, which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo. ... Amniocentesis, or an Amniotic Fluid Test (AFT), is a medical procedure used for prenatal diagnosis, in which a small amount of amniotic fluid is extracted from the amnion around a developing fetus. ... The amniotic sac is a tough but thin transparent pair of membranes which holds a developing embryo (and later fetus) until shortly before birth. ... Fetoscopy is an endoscopic procedure during pregnancy to allow access to the fetus, the amniotic cavity, the umbilical cord, and the fetal side of the placenta. ...

See also

Genetic counseling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning in order to prevent, avoid or...

References

  1. ^ Baby Gender Mentor™ Home DNA Gender Testing Kit. The Pregnancy Store website. Retrieved on 2006-07-18.

For the Manfred Mann album, see 2006 (album). ... July 18 is the 199th day (200th in leap years) of the year in the Gregorian calendar, with 166 days remaining. ...

External links

  • Special non-invasive advances in fetal and neonatal evaluation network

  Results from FactBites:
 
eMedicine - Prenatal Diagnosis for Congenital Malformations and Genetic Disorders : Article by Daljit Singh, MS, DSc (4466 words)
Prenatal diagnosis of retinoblastoma cases with deletion of this band on chromosome 13 is feasible using fluorescent-labeled probes for this region.
Prenatal diagnosis for congenital malformations and genetic disorders.
Anton-Lamprecht I: Genetically induced abnormalities of epidermal differentiation and ultrastructure in ichthyoses and epidermolyses: pathogenesis, heterogeneity, fetal manifestation, and prenatal diagnosis.
BioMed Central | Full text | Prenatal diagnosis of Caudal Regression Syndrome : a case report (1271 words)
Prenatal ultrasonographic diagnosis of caudal regression syndrome is possible at 22 weeks' of gestation by ultrasound examination.
In sirenomelia third-trimester ultrasonographic diagnosis is usually impaired by severe oligohydramnios related to bilateral renal agenesis, whereas during the early second trimester the amount of amniotic fluid may be sufficient to allow diagnosis.
Early antenatal sonographic diagnosis is important in view of the dismal prognosis, and allows for earlier, less traumatic termination of pregnancy [5].
  More results at FactBites »

 
 

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