Diagnostic tests are used to confirm abnormalities in the fetus, and are generally used after screening tests or ultrasound scan have shown that you may be at high risk. The main diagnostic tests are amniocentesis and chorionic villus sampling (CVS). Amniocentesis is the most common diagnostic test; CVS is not available in all centres, and it carries a higher risk of miscarriage.
Diagnostic tests in pregnancy: Amniocentesis
Amniocentesis is the name given to the procedure that withdraws this amniotic fluid from the uterus. Amniotic fluid contains cells from the baby’s skin and other organs, which can be used to diagnose his condition.
Diagnostic tests in pregnancy: Chorionic villus sampling (CVS)
Chorionic villi, finger- like outgrowths on the edge of the chorion are genetically identical to fetus. They develop earlier than amniotic fluid, so examining a sample of Chorionic villi provides valuable information about your baby’s genes and chromosomes before it is possible to carry out amniocentesis.
Diagnostic tests in pregnancy: Umbilical vein sampling (Cordocentesis)
This procedure is used to check the makeup of fetal blood and, in cases of fetal anaemia, for intrauterine blood transfusion. It is also used to check for infections and to assess your baby’s level of hemoglobin. Umbilical vein sampling (Cordocentesis) is no longer used in cases of suspected slow growth. Instead, Doppler scan provide the necessary information and these are available in most units.
Diagnostic tests in pregnancy: Doppler scan
This is a special scan, now available in most units. The Doppler scan uses black and white or color images to look at the blood flow between the placenta and your baby through the umbilical cord. Doppler uses slightly different sort of soundwave from a normal ultrasound scan, which bounces off moving red blood cells and shows how fast they are moving through the fetus’s blood vessels. Doppler is used to check when a baby is small for dates or seems not to growing as fast as it should. Doppler can be used to assess whether the developing fetus has anaemia. An anaemic baby will show an unusual pattern f blood flow around the body.
Situation like this put an enormous emotional strain for parents to be, so it is important to talk in detail to your doctor beforehand about the risk of having the tests and the implications of their results.