NIPT (Non Invasive Prenatal Test)
NIPT is performed on a maternal blood sample which contains DNA from the fetus.
During pregnancy, there are cell-free DNA fragments (cfDNA) from both the mother and fetus in maternal circulation. It is possible to analyze cell-free DNA to detect fetal trisomies such as Down syndrome (trisomy 21).
- Fetal anomalies on ultrasound
- Known genetic anomalies that cannot be diagnosed by NIPT
20 ml blood (2 tubes) from the mother has to be taken into specific blood tubes provided by GENDIA. Please fill the 2 tubes completely. The samples have to be sent in a specific kit by Express mail to GENDIA’s lab in Antwerp, Belgium, and arrive there within 2 days of withdrawal. The maternal blood can be taken from week 10 of the pregnancy.
Blood can be drawn from gestation week 10.
During pregnancy, there are fetal cells and cell-free DNA fragments (cfDNA) from the fetus in the maternal circulation. DNA isolated from maternal blood therefore not only contains maternal DNA but also a small amount of fetal DNA: the fetal fraction of cell-free DNA in maternal blood from week 10 on is about 10-15% of all cell-free DNA. It is possible to analyze this cell-free DNA to detect fetal trisomies such as Down syndrome (trisomy 21).
NIPT was developed and is performed by the ARIOSA laboratory in the USA under the Clinical Laboratory Improvement Amendments (CLIA).
Usually you receive the NIPT result through email in about 2 weeks.
The sensitivity of NIPT to exclude Down syndrome (trisomy 21) is very high: if NIPT is normal, the residual risk for trisomy 21, trisomy 18 and trisomy 13 is < 1 on 1.000. 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.
In a limited number of pregnancies (< 1,4%) not enough fetal DNA can be extracted from the maternal blood, and NIPT cannot be performed. This has no implications on the risk of fetal aneuploidies or other fetal anomalies. In these pregnancies NIPT can be repeated at no extra cost on a repeat maternal blood sample.
NIPT results will be sent to the patient and/or physician who ordered the test and who will explain the test results and recommended follow-up steps if necessary.
At that time the patient can also request to reveal the genetic sex of the baby.
- 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 test failure: in a limited number of pregnancies (< 1%) not enough fetal DNA can be extracted from the maternal blood, and NIPT cannot be performed. In these pregnancies NIPT can be repeated at no extra cost on a repeat maternal blood sample.
- In case of an abnormal NIPT result: in case of an abnormal result, the physician or genetic counseler will discuss the implications of such chromosomal anomaly with the patient, who can then decide to confirm the NIPT results with chromosome studies after amniocentesis or chorion biopsy.