NIPT – Non-invasive Prenatal Test

This special test is a screening test used to detect the risk of Down’s syndrome in an unborn baby. It has several names, the most common ones being Non-Invasive Prenatal Testing (NIPT), and Cell-free Fetal DNA Testing (CfF-DNA).

NIPT is highly sensitive and is able to detect more than 99% of cases of Down’s syndrome. Traces of the baby’s DNA circulate in the mother’s bloodstream – known as cfDNA (cell free DNA). Non-invasive prenatal testing (NIPT) is a way of examining fetal DNA by taking a sample of blood from a pregnant woman to determine the baby’s risk for a number of genetic disorders, including Down’s syndrome.

All NIPTs screen for the most common chromosomal disorders:

• Trisomy 21 (Down syndrome)
• Trisomy 18 (Edwards syndrome)
• Trisomy 13 (Patau syndrome)

NIPT also offers optional testing for other genetic conditions such as deletion syndromes and sex chromosome aneuploidies.

It can also tell you your baby’s Rh blood type and gender, so be sure to let your doctor know if you want to be surprised on delivery day!

How does the test help you?

NIPT examines the small fragments of DNA – known as cell free DNA (cfDNA), that float in the mother's blood. A portion of these cfDNA comes from the placenta and carries the DNA of the fetus.

This cfDNA of the fetus can be isolated and examined for a range of abnormalities.
By looking at the proportions of fragments it is possible to determine if they come from a person with the standard complement of 46 chromosomes, or if there are more or fewer chromosomes. The fragments can also be tested for specific genetic markers.

The test is primarily used to detect aneuploidies – where an abnormal number of chromosomes is present in each cell – specifically the trisomies that cause Down's(21), Edwards'(18) and Patau's(13) syndromes. Aneuploidy of other chromosomes can occur, but is usually associated with an early miscarriage.

Down’s syndrome: This is due to the fetus having three, rather than two, copies of chromosome 21. It is the most common aneuploidy identified at birth. Commonly seen physical signs include decreased or poor muscle tone, short neck, flattened facial profile and nose, small head, ears, and mouth, upward slanting eyes, and wide, short hands with short fingers. Cognitive impairment, problems with thinking and learning, short attention span, Impulsive behavior, delayed language and speech development are other signs seen in Down’s syndrome.

Edward’s syndrome: This is due to the fetus having three, rather than the normal two, copies of chromosome 18. It is a rare but serious genetic condition that causes a wide range of severe medical problems. Sadly, most babies with Edwards' syndrome will die before or shortly after being born.

Patau syndrome: This is due to the fetus having three, rather than the normal two, copies of chromosome 13. Trisomy 13 causes severe intellectual disability and major malformations like cleft lip or palate, clenched hands or extra fingers or toes, umbilical hernia or inguinal hernia, hole or split or cleft in the iris, skeletal (limb) abnormalities, small eyes and undescended testicles.

Sex Chromosome Aneuploidy: As fetal sex is determined by chromosomes, accurate sex determination is also possible from nine weeks gestational age - much earlier than by ultrasound. Sex chromosome aneuploidy (SCA) means aneuploidies of the sex chromosomes (X and Y) such as Turner syndrome (monosomy X - having only one sex chromosome) and Kleinfelter Syndrome (XXY - having three sex chromosomes) are also detectable. Those detected with a SCA usually have an impaired fertility issue but a normal intellectual functioning.

Turner syndrome: Turner syndrome, also known as 45,X or 45,X0, is a condition in which a female is partly or completely missing an X chromosome. Turner syndrome can cause a variety of medical and developmental problems, including short height, failure of the ovaries to develop, Diabetes. Thyroid problems and heart defects. They may demonstrate a short and webbed neck, low-set ears, low hairline at the back of the neck, and swollen hands and feet at birth. They usually need treatment to develop menstrual periods and breasts.

Microdeletions: A chromosome deletion refers to the absence of a segment of the DNA from a chromosome. Though the overall number of chromosomes is not affected, one of the chromosomes may be missing some part of its DNA. A chromosome deletion is often referred to as a ‘microdeletion’ as the segment that is missing might actually be extremely small.

One of the most common microdeletions is the one that affects the chromosome 22. It is called the 22q11.2 deletion. The deletion is so small that it is usually undetectable when using conventional screening methods. Although the microdeletion is a very small fragment, it results in the absence of a number of genes. The occurrence rate has been studied to be 1:1000 pregnancies.

After Down syndrome (trisomy 21), 22q11.2 deletion is the second most common cause of developmental delay and is the underlying cause for DiGeorge syndrome, velocardiofacial syndrome, Shprintzen syndrome and Takao syndrome. It may present as Heart defects, cleft, learning difficulties, impaired immune system, Kidney anomalies, hearing loss, laryngotracheoesophageal anomalies,Autoimmune disorders (thrombocytopenia, juvenile rheumatoid arthritis, overactive thyroid), Seizures, skeletal abnormalities, ptosis, cataract, strabismus, Developmental delay, intellectual disability autism spectrum disorders and attention deficit disorder.