FAQ

The blood sample is sent to the laboratory and results are reported to you in approximately 3-5 calendar days from receipt of the sample in the lab.

We can run samples from multifetal gestations in this pregnancy, egg donors, and IVF patients — essentially any increased risk pregnant woman.

Positive predictive vaule is the percentage of true positive results divided by the number of all positive results, and answers the question: What is the likelihood of a positive infant having a truly positive outcome?

It should be stressed that PPV in each case depends on the prevalence of the condition in the population under study. For trisomies, their frequency increases along with the mother’s age. For example, the pre-test risk for trisomy 21, 18, and 13 in a 35 year old with a fetus at 10 weeks of gestation is 1: 185, 1: 470 and 1: 1500, respectively. These, combined with the performance characteristics described above, are translated into PPVs of 87%, 58%, and 24%, respectively. As expected, in trisomy 13 that is less prevalent in the population tested, it is most likely that a positive cDNA NIPT result will be falsely positive.

By comparison, the sensitivity of the best biochemical screening test (Papp-A and β-hCG) for trisomy 21 is 93% with a 95% specificity. Therefore, a risk for trisomy 21, 1: 270, translates to PPV of only 6%. In conclusion, cfDNA NIPTs clearly outweigh the traditional biochemical tests when we detect embryonic chromosomal aneuploidy.

Despite their excellent clarity, cfDNA NIPTs do not produce definitive results. Thus, just as with a positive screening assay with biochemical markers, a positive result from NFT cfDNA should be followed by invasive diagnostic methods.

Chromosomes are structures inside every cell of your body. They hold the genes, inherited from your mother and father, which tell your body how to grow and develop. Most people have 23 pairs of chromosomes, each carrying thousands of genes. The first 22 pairs are called the autosomes, and are identical in males and females. The 23rd pair is the sex chromosomes – X and Y. Females usually have two X chromosomes; males have one X chromosome and one Y chromosome.

Some people are born with an extra or missing chromosome, meaning they have three copies of a chromosome instead of two. This is known as a trisomy. The most common fetal trisomies are trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome).

Some chromosome changes, like22q (DiGeorge syndrome), 15q (Angelman/Prader-Willi syndromes), 11q (Jacobsen syndrome), 8q (Langer-Giedion syndrome), 5p (Cri-du-chat syndrome), 4p (Wolf-Hirschhorn syndrome), and 1p36 deletion syndrome, don’t involve whole chromosomes, but small pieces of chromosomal material instead. These types of changes can cause specific traits or characteristics to occur in your unborn baby. These conditions are very rare. They can be diagnosed using an invasive procedure called CVS or amniocentesis if there is a suspicion following other prenatal testing. Discussing with your health care provider the risk of having a baby with one of these conditions is encouraged if testing identifies a risk.

Anyone can have a pregnancy with a chromosomal abnormality – mothers of all ages, races and health conditions can be at risk.

There is nothing a parent can do to cause a chromosomal abnormality, or prevent it. However, certain risk factors can increase the chance of having a pregnancy with chromosomal abnormalities.

These include:

• Advanced maternal age.
• Fetal ultrasound abnormality suggestive of chromosomal abnormalities.
• Personal or family history of chromosomal abnormalities.
• Positive serum screening test.

Down syndrome is a condition caused by an extra copy of chromosome 21. Children with Down syndrome have intellectual and developmental impairment. Babies with Down syndrome also have higher chances for certain health problems. Not everyone with Down syndrome is affected in the same way, and there is no way to determine before birth how a child may be affected. Down syndrome affects about one in every 700 babies. The chance of having a child with Down syndrome increases with the woman’s age, but women of all ages and races may be at risk.

Edwards syndrome is caused by an extra copy of chromosome 18. Babies with trisomy 18 often have multiple birth defects, and many don’t survive the first few months of life. Survivors have serious health problems and typically do not walk or talk. About one in every 5,000 babies is born with trisomy 18.

Patau syndrome is caused by an extra copy of chromosome 13. These babies have multiple birth defects and often don’t survive the first few months of life. Survivors are profoundly intellectually and developmentally impaired. This condition is less common than Down or Edwards syndrome and occurs in about 1 in 16,000 babies.

The sex chromosomes, X and Y, are associated with gender. Females typically have two X chromosomes and males have an X and a Y. Abnormalities in the number of sex chromosomes do not usually cause substantialdevelopmental and intellectual impairment. Early diagnosis can help these children get services as needed in order to reach their full potential. Overall, about one in every 500 babies is born with a sex chromosomal abnormality.

Most girls with Turner syndrome have only one copy of the X chromosome. Many of these pregnancies are miscarried during pregnancy. Girls with Turner syndrome are usually shorter than average, have delayed or absent puberty and may be infertile. Most have normal intelligence, but some have learning difficulties. Children with Turner syndrome may also have heart or kidney defects. Identifying these abnormalities should prompt consideration of medical (endocrinologic) therapy in childhood.

Boys with Klinefelter syndrome have two X chromosomes and one Y. These boys tend to be taller than average, may have delayed or absent puberty and are often infertile. Most have normal intelligence, but some may have learning or psychological difficulties.

Children with either of these conditions may be taller than average and usually have normal intelligence. A few may have learning or psychological issues. These conditions are not associated with birth defects and may go undiagnosed. People with these conditions may have normal fertility.  Identifying these abnormalities should prompt consideration of medical (endocrinologic) therapy in childhood.

Trisomy 16 is one of the most common causes of miscarriage. It is caused by an extra copy of chromosome 16. Many pregnancies with trisomy 16, unfortunately, do not continue to term. In rarer instances, babies with trisomy 16 can also have some cells with normal numbers of chromosomes. This is called a mosaic result. Trisomy 16 and mosaic trisomy 16 have a significant risk for miscarriage, pregnancy complications like growth delay, and other abnormal outcomes.

Trisomy 22 is a common cause of miscarriage. It is caused by an extra copy of chromosome 22. Many pregnancies with trisomy 22, unfortunately, do not continue to term. In rarer instances, babies with trisomy 22 can also have some cells with normal numbers of chromosomes. This is called a mosaic result. Mosaic trisomy 22 also has a significant risk for miscarriage.

22q11.2 deletion syndrome, or 22q for short, is a rare chromosome change with chromosome 22. A small piece of the chromosome is deleted, or missing. This piece of the chromosome contains many numbers of genes. Missing this piece of chromosome 22 causes health problems like heart defects, palate, or roof of the mouth defects, immune problems, learning delays, or other types of traits.

Cri-du-chat syndrome is a rare condition named for a unique, high-pitched cry in affected children. It is caused by a missing piece of chromosome 5. This is sometimes called 5p-, or 5p minus. Cri-du-chat is French for the term, “cry of the cat”, as these children have distinctive cries. Other symptoms, such as poor muscle tone, difficulty with speech, and intellectual disability can occur.

A set of conditions is related to changes that take place on chromosome 15. Prader-Willi syndrome and Angelman syndrome are two conditions caused by a missing piece of chromosome 15. Most instances of Prader-Willi or Angelman syndrome are caused by a deletion of a part of chromosome 15. Depending on how the missing piece of chromosome 15 was inherited can determine what kind of traits a child will have.

Missing a piece of chromosome 1 can cause a condition called 1p36. This chromosome change can result in poor muscle tone, difficulty with speech, characteristic facial appearances, and intellectual disability.

Jacobsen syndrome is a rare condition caused by a missing piece of chromosome 11. Some features of Jacobsen syndrome include short stature, intellectual disability and distinctive facial features. Many can experience bleeding disorders and malformations of the heart as well. Jacobsen syndrome is not a frequent occurrence, with approximately 1 per 100,000 children diagnosed.

Langer-Giedion syndrome (Tricho-rhino-phalangeal syndrome type II) is caused by a missing piece of chromosome 8. This condition is characterized by bone growths (exostoses), short stature, skeletal or bone findings, and distinctive facial features. Mild to moderate intellectual disability has been reported. This diagnosis is quite rare. Estimates of the frequency of this diagnosis are not well understood.

Wolf-Hirschhorn syndrome (4p minus) is caused by a missing piece of chromosome 4. This condition is characterized by distinctive facial features, growth delays, intellectual disability, hearing loss and seizures. This is a rare diagnosis, with approximately 1 diagnosis per 50,000 births.

No test is perfect. While results of the MaterniT21 PLUS test are highly accurate, false positive and false negative results may occur in rare cases. DNA test results do not provide a definitive genetic risk in all individuals. Cell-free DNA does not replace the accuracy and precision of prenatal diagnosis with CVS or amniocentesis. A patient with a positive test result or the presence of an Additional Finding should be referred for genetic counseling and offered invasive prenatal diagnosis for confirmation of test results. A negative test result does not ensure an unaffected pregnancy. The absence of an Additional Finding does not indicate a negative result. While results of this testing are highly accurate, not all chromosomal abnormalities may be detected due to placental, maternal or fetal mosaicism, or other causes. Sex chromosomal aneuploidies are not reportable for known multiple gestations. The health care provider is responsible for the use of this information in the management of their patient.