Methodology of prenatal testing is typically dependent on what the test is attempting to determine. Some prenatal testing involves blood tests, while others may make use of sonograms or other image mapping techniques. In some cases, prenatal testing may require drawing fluid from the amniotic sac, through a process called amniocentesis. Prenatal testing is used for several different reasons, including genetic screening, establishment of paternity, and to determine the health of a fetus.
In some cases, it may be necessary to establish the identify of the father of an unborn child. In this type of situation, doctors typically need a sample of amniotic fluid to conduct tests on deoxyribonucleic acid (DNA). This allows them to determine if there is a DNA match between the possible father and the fetus. This is usually done by amniocentesis, which can be painful and invasive, and can put the fetus and the mother at risk. In some countries, amniocentesis is not allowed for purposes of paternity.
Medical research has developed many ways to determine if a particular fetus might be at risk for certain types of conditions or diseases. This is especially true in diseases or conditions that are considered hereditary. This type of prenatal testing is commonly referred to as genetic testing. Genetic testing involves drawing blood from both parents, and then testing the blood for genetic markers. In some cases, amniocentesis testing may be required, depending on the type of disease involved.
Some types of prenatal testing are considered quite non-invasive, such as sonograms and ultrasounds. These tests allow doctors to actually see inside the womb and visually monitor the growth and development of the fetus. Doctors typically gain much of the information they need to determine the health of the baby through these visual inspections. In normal pregnancies, doctors typically order about four sonograms, one during each trimester of the pregnancy, and one near delivery time. In pregnancies where the fetus is considered to be at higher risk, these tests are typically done more frequently.
Other less common types of prenatal testing include chorionic villus sampling (CVS) and nuchal translucency (NT) testing. CVS is an invasive type of test that involves removing a tiny sample of tissue from the placenta. This test is usually done to determine if abnormal chromosomes are present. NT testing is usually performed to determine if the fetus has Down’s syndrome. These types of tests are typically not ordered unless there are specific reasons to indicate that the possibility of abnormal chromosomes exists.