DNA Based Prenatal Test (NIPT test)

DNA Based Prenatal Test:

• It is a non invasive test.
• Most sensitive screening option for detecting trisomy 21, 18, and 13.
• It is done as early as 10th week of pregnancy.
• Looks for fragments of the fetus’s DNA in the mother’s blood.
• It is a single blood draw from the mother.
• Can also identify the fetus’s sex. (Read more: Gender Selection)
• Takes 7-14 days until receiving the final report.
• Yet not endorsed for twin pregnancies.

For:
Evaluating the risk of possible chromosomal conditions such as:

• Down syndrome/ trisomy 21
• Edward’s syndrome/trisomy 18
• Patau syndrome/trisomy 13
• Monosomy X
• Sex chromosome aneuploidy

NIPT Test indications:

• Advanced maternal age (35 years old and more)
• Positive serum screen result
• Previous affected pregnancy
• Abnormal fetal ultrasound findings
• A parent carries a relevant Robertsonian translocation

But recent studies suggested that the test is recommended for for all pregnant women regardless of age or risk.

Advantages:

• It can be done as early as 10 weeks of pregnancy.
• No pregnancy loss risk comparing to other traditional screenings.
• Accuracy:
  • a. Trisomy 21: DR (Detection Rate) 99.5%, FPR (False Positive Result) 0.05%
  • b. Trisomy 18: DR 97.7%, FPR 0.04%
  • c. Trisomy 13: DR 96.1%, FPR 0.06%

1 – 5% possibility that the test does not yield a result.

Also, obese women (weight over 81 kg) are at increased risk of receiving a test failure.

What if the results are positive?
Invasive diagnostic testing must be performed to confirm the results.