What is Non-invasive Prenatal Test (NIPT)?
NIPT, also known as Non-invasive Chromosomes Check, is a prenatal test that screens fetuses for Down syndrome. Down syndrome (Trisomy 21) is a genetic disorder whereby there are three pairs of Chromosome 21 in the human’s cells: instead of the normal two pairs.
Down syndrome can happen in any pregnancies, but it is more common among women who conceived after 35-year-old. Various laboratories offer NIPT testing for pregnant mothers. NIPT detects Down syndrome with a very high detection rate of over 99 percent.
Besides Down syndrome, NIPT can also screen for other chromosomal abnormalities and genetic syndromes, but the detection rate is not high. NIPT can be done as early as 9 weeks during pregnancy. A simple blood sample taken from the pregnant mother is all that is needed. The results will usually be available within 14 days.
Women with low-risk results can also be reassured
For those with high-risk results, invasive prenatal tests including Chorionic Villus Sampling (CVS, sampling of the placenta tissues) or Amniocentesis (sampling of the amniotic fluid) will be required for confirmation.
The importance of early pregnancy detection
Early pregnancy detection is important as it allows early confirmation of the genetic disorder. It enables early introduction of prenatal treatment, if available, or termination of the pregnancy, if indicated. Having the result in the first trimester also provides closure and allays parental anxiety. Besides, early pregnancy detection assists in the preparation and plan of delivery. The result is important as it can facilitate the determination of the risk of recurrence in subsequent pregnancies.
How NIPT works
During pregnancy, fetal DNAs are released from the placenta and circulate in the mother’s bloodstream.
Fetal DNAs are detectable in the mother’s circulation as early as 9 weeks of pregnancy and continue to increase as the pregnancy advances. By withdrawing the mother’s blood, screening for Down syndrome can be conducted for the fetus.
The Benefits of NIPT
NIPT is an excellent screening tool for Down syndrome, as it has a very high detection rate. It is a safe test, and it can be done by a simple blood sample drawing. Only 10mls of the mother’s blood is required for the test.
NIPT is non- invasive and avoids the risk of miscarriages (about 0.5-1 percent) in Chorionic Villus Sampling and Amniocentesis procedures.
The Limitations of NIPT
NIPT is not a diagnostic test. Patients who are screened as high risk are required to have Chorionic Villus Sampling or Amniocentesis for confirmation. NIPT does not eliminate all chromosomal abnormalities and genetic syndromes. NIPT also does not detect other complications in the fetus and pregnancy.
The detection rate of Down syndrome for twin pregnancies is lower than a singleton pregnancy. NIPT is not recomended for triplet and other higher order pregnancies.
Who should consider NIPT:
- All pregnant women
- Pregnant women who are anxious and want to know their baby’s health
- Women who are more than 35 year-old
- Pregnant women whose previous child/children have Down Syndrome
- Those whose family members have Chromosomal abnormalities and genetic syndromes
- When a fetus indicates an abnormal Nuchal Translucency (NT), or when combined test are recomended
Dr Lim Wan Teng
Consultant Obstetrician & Gynaecologist, Maternal Fetal,
Pantai Hospital Cheras Medicine Specialist
