What is Prenatal Diagnosis?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 21 March 2018
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Prenatal diagnosis is a diagnosis or ruling out of health issues with a fetus. This occurs at different times during a pregnancy, by various types of diagnostic tools. Most women who have ultrasounds have been part of a prenatal diagnosis attempt. In the majority of instances, there is nothing to diagnose and women go on to deliver healthy babies. In other cases, health conditions are detected during the pregnancy via ultrasound or other screening tests.

There are a number of optional screening tests available during pregnancy. Many believe that in apparently healthy pregnancies, where there is no genetic history of health problems, it isn’t necessary to utilize any of these tests. Some of them, like amniocentesis and chorionic villus sampling, pose some risk to the fetus and pregnancy, though they can identify conditions like Down syndrome or other genetic disorders.

This type of fetal diagnosis is considered useful for a couple of reasons. It allows mothers to consider abortion or a child with severe genetic defects or to take the time to educate and prepare themselves for a child who will have issues after birth. Since conditions like Down’s can be associated with a higher rate of dangerous birth defects like congenital heart defects, a planned birth at a tertiary hospital could address early problems more effectively.

Another way to perform prenatal diagnosis is through a maternal blood test. Such tests might reveal if there are incompatibility problems between maternal and fetal blood, or some blood testing may be able to detect genetic problems of the fetus. In recent years, doctors have isolated methods for testing maternal blood to look at fetal DNA, and research suggests such methods may replace the more invasive types of testing that are used today.

Non-invasive tools to evaluate and diagnose a fetus include ultrasound and the more refined fetal echocardiogram. Ultrasound evaluates a number of features and could be useful in prenatal diagnosis if growth is insufficient or if there are missing structures, among other things. A pregnancy can also be diagnosed as a miscarriage if it is found that the fetus has died in utero.

The fetal echocardiogram is similar to the fetal ultrasound, but looks specifically at the structures of the heart. Since heart defects are the most common birth defects, it is surprising that this test is not routinely offered to most women. Generally, it would only be offered if a routine ultrasound comes up with a potential prenatal diagnosis of heart problems. Since some of these problems are complex, they’re not always by noticed ultrasonographers.

Fetal diagnosis isn’t always completely accurate, and it may change as the pregnancy progresses. Doctors use this time to continue gathering information about fetal health, to plan the best strategy for medical care after birth. Though rare, there are now some instances when a fetal diagnosis means having treatment right away. Fetal surgeries may be able to repair problems before the baby is born.



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