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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. There are both invasive and non-invasive methods of diagnosing a problem before birth. Examination of the mother's womb through ultrasonography are routinely done to check for any abnormality in the pregnancy. If an abnormality is indicated by a non-invasive procedure, a more invasive technique may be employed to gather more information. 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. 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. As well as this, it gives the option of abortion of the fetus. Healthcare staff can also 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 is often more favorable. This 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. An estimated 50-70% of expectant parents would like to know the gender of their child ahead of delivering the baby.• Some parents would like to know this information early in order to get a head start on shopping for baby clothes or decorating the nursery.• Others have cited an interest in preparing themselves or the baby's siblings for gender-specific issues.• Risk factors qualifying a woman for prenatal testing Ethical issues of prenatal testing 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. 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. 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. 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. Some say the argument not to have prenatal diagnosis is a Right-to-life argument. Pro-life activists believe that “because in utero treatment is in its infancy, prenatal diagnosis today is used to seek out and destroy ‘defective’ infants. However, this view assumes that the goal of prenatal diagnosis is simply to abort abnormal pregnancies. Some believe that knowing about a baby's health problems before birth can prepare the family, allow them to make informed decisions about treatment or surgery options, and alert the medical professionals who would be caring for the abnormal baby. Also, many women decide not to have prenatal diagnosis because of the risks of complications associated with the invasive procedures. It is the decision of the pregnant woman whether to have testing and what to do with the information if the results show a problem. Methods of prenatal diagnosis Non-invasive methods: (to the baby) Invasive methods: See also | |||||||
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