About Prenatal Testing
DNA from the fetus circulates in the mother’s blood. Cell-free DNA (cfDNA) results from the natural breakdown of fetal cells (presumed to be mostly placental) and clears from the maternal system within hours of giving birth.
During a pregnancy, cfDNA can be tested to give the most accurate screening approach in estimating the risk of a fetus having a common chromosome condition sometimes called a trisomy. This occurs when there are three copies of a particular chromosome instead of the expected two. The test looks to detect the following trisomies:
- Trisomy 21 is the most common trisomy at the time of birth. Also called Down syndrome, it is associated with moderate to severe intellectual disabilities and may also lead to digestive disease, congenital heart defects and other malformations.
- Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome) are associated with a high rate of miscarriage. These babies are born with severe brain abnormalities and often have congenital heart defects as well as other birth defects. Most affected individuals die before or soon after birth, and very few survive beyond the first year of life.
- Sex chromosome conditions. The sex chromosomes (X and Y) determine whether we are male or female. X and Y chromosome conditions occur when there is a missing, extra, or incomplete copy of one of the sex chromosomes. The Harmony with X, Y test can assess risk for XXX, XYY, XXYY, XXY (Klinefelter syndrome), and a missing X chromosome in a girl (Turner syndrome). There is significant variability in the severity of these conditions, but most individuals have mild, if any, physical or behavioural features. If the mother is interested in having this optional testing, she should talk with her healthcare provider to determine if it is right for her. This option is not available for twin pregnancies.
This test is non-invasive as it involves taking a blood sample from the mother only.
The pregnancy is not put at risk of miscarriage or any other adverse outcomes that are associated with invasive testing procedures such as amniocentesis.
Clinical studies have shown that the Prenatal testing has up to 99% accuracy for assessing fetal trisomy risk.
Who can have the test?
The Prenatal testing in Cork – Prenatal Test can be done by the GP for women with pregnancies of at least 10 weeks’ gestational age. The test can also be done for all IVF singleton pregnancies, including those with egg donors. Samples from pregnant women with twins naturally conceived, or those conceived using the patient’s own egg, are also accepted.
How long will I have to wait for results?
The test is sent to Dublin/London for processing. At the moment we are advised that the turnaround time is 7 – 10 working days.