Non-Invasive Prenatal Testing

Non-Invasive Prenatal Testing

Non-Invasive Prenatal Testing

NIPT is a genetic test for Trisomy 21 (Down Syndrome), Trisomy 13 and Trisomy 18, as well as testing of the gender chromosomes, using fetal DNA in maternal blood.

The main benefit of NIPT is that it has a 99.5% success rate in detecting Down Syndrome in the fetus. Nuchal translucency programme has a 90-95% accuracy in detecting aneuploidy such as Trisomy 13, 18 and 21. Non-invasive prenatal testing (NIPT) or Amniocentesis should be considered for higher accuracy. The detection for Trisomy 13 and 18 ranges from 96-99%.

NIPT can be performed for twin pregnancies although the reliability is less than for singleton pregnancies. There is a small failure rate of the NIPT test depending on the amount of fetal DNA that can be detected in the mother’s blood sample. It is important to note that approximately 25% of chromosome abnormalities in pregnancy, as well as major structural anomalies, are not detected by a NIPT test. A 12-14 week first-trimester fetal morphology scan is recommended as part of your first-trimester screening with NIPT.

This will give an opportunity for other chromosome or structural changes to be diagnosed. As NIPT is a screening test, a non-conclusive result, or a positive result on NIPT should be followed up by chorionic villous sampling (CVS), or amniocentesis.

What is a nuchal translucency scan?

The nuchal translucency scan is a non-invasive ultrasound which is performed to measure the amount of fluid present on your baby’s neck, and determine if there is any excess fluid. This assessment is important as it helps in the diagnosis of potential fetal complications, including Down Syndrome. If our specialists detect any abnormalities, we will notify you of the risks, and discuss your options with you. Counselling and recommendations for non-invasive prenatal testing, or definitive tests such as amniocentesis or CVS (invasive confirmation of chromosomal complications) can be offered. When is it recommended, and how is my risk factor calculated? The nuchal translucency scan is recommended between 12-14 weeks gestation, as this is the stage of the pregnancy when the thickness of the nuchal translucency fluid can be seen to be different from a chromosomally normal fetus.

The chromosomal risk is calculated using:

  • The mother’s age
  • The Nuchal translucency thickness in the fetus, and the presence of the nasal bone.
  • The mother’s serum level of beta-hCG and PAPP-A

An assessment is also made of the fetal heart, including tricuspid regurgitance and blood flow in the fetal vessel ductus venous, as these are also used in decision-making. Uterine artery Doppler assessment and Preeclampsia Screening are also available at the time of this scan.

For further information on these scans, download one of our full information pack below.

First Trimester Screening Options

Invitae NIPT Condition Descriptions

General Patient Brochure

NIPT Options Flyer

Nuchal Translucency Scan Sydney NSW