Pregnancy is the most beautiful time in a woman’s life. You have a cute little bundle of joy growing inside you, and yes we know you want what is best for your little one. Though, it sometimes gets confusing with all the changes a pregnant woman has to make in her life – the numerous restrictions, diet charts and doctors’ visits with a hundred and one tests. Most times, the tests are very difficult to understand and differentiate between. Like many mothers out there, you too might have wondered what might be the difference between a screening and a diagnostic test. Don’t fret, as we’re here to help you understand the difference between the two.
Most expectant mothers undergo screening tests and their main aim is to detect potential disease indicators. Screening tests are noninvasive and increasingly accurate. Performing screening tests is not a risk to the mother or child, and they can provide a lot of valuable reassurance. Prenatal screenings, including your nuchal translucency screening test, level 2 ultrasound, initial blood workup, noninvasive prenatal test (NIPT) and the quad screen, use a sample of your blood and/or an ultrasound to check if you are at an bigger risk of giving birth to a child with a genetic disorder such as Down syndrome or a neural tube defect like spina bifida. However, they cannot diagnose any of these conditions, but can only assess the probability that a fetus is affected with anywhere from 80% to 99% accuracy in the results, based on the screening and the condition. These tests are generally simple and simply indicate suspicion of disease, in combination with other risk factors, which warrants confirmation. The tests are usually cheap as larger populations of women are required to carry out these tests.
While almost all expecting mothers require screening tests, diagnostic tests aren’t for everyone. Only those expecting mothers whose screening tests come back positive require a follow up diagnostic test to see if an abnormality actually exists. Diagnostic tests are very different from screenings and are performed to establish the presence/absence of a disease. Diagnostic tests like chorionic villus sampling (CVS) and amniocentesis analyze the genetic material in cells collected from a baby’s own placenta or amniotic fluid. The tests are much more precise and detect chromosome abnormalities like Down syndrome and neural tube defects by testing your baby’s own cells for problems and not just signs that point to possible problems or abnormalities. These tests provide a definite diagnosis and are usually of a higher cost. Keeping certain conditions in mind, your healthcare provider might recommend skipping certain screenings and order a diagnostic test first. This is usually if either you or your partner have a family history and/or is a known carrier of a genetic disorder, if you’ve previously given birth to a child with a chromosomal disorder, or if you’ve been exposed to an infection or substance that could possibly cause harm to a developing baby. Any of the cases might call for a diagnostic test prior to a screening test.