NIPT is the new Non-Invasive Prenatal Test on maternal blood to safely and reliabily screen pregnancies for the most common fetal chromosome anomalies Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome) and Trisomy 13 (Edwards syndrome).
Also the sex of the baby is determined.
NIPT is much more reliable than the classical first trimester screening or triple test. Furthermore, NIPT is much safer than the invasive test procedures such as amniocentesis and chorionic villus sampling, which have a miscarriage risk of 1%.
- Trisomy 21 (Down syndrome)
This is caused by an extra copy of chromosome 21 and is also called Down syndrome. This is the most common genetic cause of intellectual disability. Individuals with Down syndrome have some degree of intellectual disability (average IQ of 50). Some children with Down syndrome have congenital defects of the heart or other organs that may require surgery or medical treatment. Some have other medical conditions including hearing or vision loss, and at a later age dementia.
- Trisomy 18 (Edwards syndrome)
This is caused by an extra copy of chromosome 18 and is also called Edwards syndrome. Most babies with trisomy 18 have multiple severe birth defects of the brain, heart and other organs. Poor growth during pregnancy is common and many babies are miscarried or stillborn. Of those babies born alive, most die before one year of age. Babies who survive have profound intellectual disabilities and growth and developmental problems.
- Trisomy 13 (Patau syndrome)
This is caused by an extra copy of chromosome 13 and is also called Patau syndrome. Most babies with trisomy 13 have multiple severe birth defects of the brain and other organs. Many babies are miscarried or stillborn. Of those babies born alive, most die before one year of age.
- The sex of the baby is determined and is reported upon request
NIPT samples are analyzed for trisomy of chromosomes 21, 18, 13, and gender of the baby.
Aneuploidy of other chromosomes, other chromosome anomalies (including mocaicism for chromosomes 21, 18, 13), and triploidy, molecular anomalies or congenital anomalies including neural tube defects cannot be excluded.
The reliability of NIPT results is very high (> 99 %), but not 100 %, which is also the case for amniocentesis and chorionic villus sampling.
The sensitivity of NIPT to exclude trisomy 21, 18 and 13 is very high: if NIPT is normal, the residual risk for trisomy 21, trisomy 18 and trisomy 13 is < 1 on 1.000 (false-negatives).
The specificity of NIPT for the chromosomes tested is > 99%, which means that in less than 1 on 100 pregnancies an abnormal NIPT result is obtained although the fetus has normal chromosomes (false-positives).
The first trimester Down screening test (FTS) combines biochemical parameters in maternal blood with ultrasound parameters of the fetus. The biochemical tests are PAPP-A (Pregnancy Associated placental protein-A) and free beta-HCG (Human Chorionic Gonadotrophin). These values are combined with ultrasound measurements of the nuchal translucency (NT), a translucent spot in the neck of the fetus and crown-rump length (CRL) of the fetus. The blood parameters PAPP-A and free beta-HCG can be performed in week 9-11, whereas the NT should be performed in week 12-13. The 1st trimester Down screening is not a diagnostic test, but a screening test which only indicates the risk for Down syndrome.
The sensitivity and specificity of the FTS test are low:
- Sensitivity: more than 20 % of the fetal trisomies escape detection by the FTS (False-negative test): this means the FTS test is normal, but the baby has a trisomy.
- Specificity: More than 95 % of the FTS tests are false-positive : this means the FTS test is abnormal, but the baby has no trisomy.
For NIPT only blood from the mother is required. No sample from the father is necessary, unless a NIPT for cystic fibrosis, sickle cell anemia or beta thalassemia is requested. The sample has to be sent by Express mail to GENDIA’s lab in Antwerp, Belgium, and arrive there within 2 days of withdrawal.
The kits and blood tubes have to be kept at room temperature.
NIPT results (in English) will be sent by email to you, your midwife and physician (please provide all email addresses on the patient form that goes with the sample). The result will say NORMAL or ABNORMAL (in case of trisomy 21, 18 or 13 ).
When you indicated on the patient form you wanted to know the sex of the baby, this will be mentioned in the report. When you did not indicate this, you can request the sex of the baby by email (NIPT@GENDIA.net) without extra cost. In case of a normal NIPT result no specific follow up is necessary unless ultrasound examination of the fetus reveals anomalies and further fetal studies might be indicated.
In case of a trisomy of chromosome 21, 18, or 13, the implications will be discussed with you by your physician, midwife or Dr Willems from GENDIA. You can then decide to confirm the NIPT results with amniocentesis or chorionic villus biopsy (CVS), and discuss with the gynecologist whether you want to interrupt the pregnancy.
You find an example of a NIPT report HERE.