What is Fetal Fraction NIPT?

Being pregnant is an incredible experience full of joy, hope, and a desire to protect the developing life inside of you. Pregnant women are now given access to sophisticated prenatal screening tests that offer priceless insights about the genetic health of their unborn child, thanks to advancements in medical science. One such test that has completely changed the prenatal care landscape is the non-invasive prenatal test (NIPT), which provides a reliable and accurate way to determine a woman’s chance of developing specific abnormalities in her chromosomes. Fetal fractions are the fundamental component of this test and is an important aspect that greatly influences the accuracy and dependability of the NIPT results.

What Does Fetal Fraction Mean?

The amount of cell-free DNA (cfDNA) from the birth canal and, consequently, the growing fetus in a pregnant mother’s blood is referred to as the fetal fraction or fetal fraction percentage. Some genetic material from the developing baby regularly passes through the placental membrane and enters the mother’s circulation throughout pregnancy. NIPT tests primarily investigate this fetal DNA, which differs from the mothers.

One of the most crucial aspects of prenatal testing is checking for fetal aneuploidy or other genetic abnormalities. Until recently, chorionic villus sampling (CVS) and amniotic fluid testing were used to screen a fetus genetically. Nevertheless, there is a chance that these tests will result in infection and miscarriages with rates of 0.5% and 0.1 – 0.3%, respectively.

What Is Fetal Fraction Percentage?

The quantity of fetal DNA contained in the entire cell-free DNA sample extracted from the maternal bloodstream is known as the fetal fraction percentage, and it is commonly reported as a numerical figure. When the fetal fraction in the specimen is 10%, it indicates that 10% of the cfDNA comes from the developing baby and the other ninety percent comes from the maternal cells.

What Does Fetal Fraction Mean on NIPT?

The fetal fraction is a significant factor when assessing the accuracy and dependability of the results in NIPT examinations. A more significant fetal percentage typically denotes a higher degree of confidence in the test’s capacity to identify the fetal sex or identify chromosomal defects precisely. On the other hand, a lower fetal proportion could produce outcomes that are less trustworthy or inconclusive.

Fetal Fraction and Test Failure:

Face DNA’s cfDNA NIPT methods that rely on microarrays and focused sequencing, a minimum fetal fraction cutoff is used. If the fetal fraction of the sample is less than this cutoff, no result or test failure is reported. Even after redrawing, strict fetal fraction cutoffs increase test failure rates. Furthermore, even though the labs have paid for the test, they are frequently not compensated when it yields no results.

What Is a Good Fetal Fraction?

The majority of medical professionals like Face DNA Testing services and laboratory recommendations recommend that a fetal sex fraction of 4% or more is sufficient for accurate NIPT results, even though there is no widely agreed-upon ideal fetal fraction. Nevertheless, it’s crucial to remember that every laboratory may have varied criteria depending on its testing procedures and approaches.

What Does Low Fetal Fraction Mean?

Proper interpretation of the NIPT data may be difficult in cases where the fetal fraction is low, usually less than 4%. In certain situations, the test may produce an inconclusive or “no-call” result, indicating that the testing facility was unable to confidently confirm the fetal sex or gain an accurate understanding of the fetus’s genetic composition.  A significant factor influencing the precision of NIPS (Non-invasive prenatal screening)  in detecting chromosomal anomalies is FF. To guarantee that there is enough cffDNA in maternal plasma to produce accurate results, FF assessment at the time of NIPS is advised as a crucial component of quality control and statistical reliability determination. In most cases, an FF of 2-5 percent is the minimal requirement that must be met for facilities such as Face DNA atto produce reliable NIPS data.

The meanings of exceptionally high and low Fetal Fractions vary. An increased probability of aneuploidy, ranging from 2.7 to 23.3%, may be indicated by a low FF. A sample is classified as a “no-call” result if its FF falls below the predetermined level; these results usually have a 2–5% rate. As a result, choosing an FF threshold necessitates making a trade-off between reducing the failure rate and increasing NIPS’s statistical dependability. Pregnant women with an FF of less than 4% had a considerably increased frequency of an abnormal pregnancy.

Good Fetal Fraction for NIPT

As previously indicated, a fetal fraction of 4% or greater is typically considered adequate for accurate non-invasive pregnancy tests. To guarantee better accuracy and lower the possibility of false-positive or false-negative findings, reputed DNA testing businesses such as Face DNA Test might favor higher thresholds, like 8% or even 10%.

How Much Fetal Fraction Is Needed for Gender?

Since the NIPT testing service at Face DNA Test requires a smaller fetal percentage than chromosomal abnormality detection, identifying fetal sex is usually more accurate. Fetal fractions that are as low as between two and three percent can typically be used by most laboratories to successfully establish the sex of the fetus, while larger fractions are recommended for greater confidence.

Sex determination can be assumed to be correct for all pregnancies when the fetal fraction is above 10% and will be accurate in more than 50% of cases when above 6% when accounting for the variation in the normalized Y chromosome readings. Additionally, we questioned whether there would be any differences in the fetal fraction calculation between twin pregnancies involving solely female fetuses or exclusively male fetuses, of male–female fetuses. As anticipated, there was no discernible difference between these groups.

Why Is There Not Enough Fetal DNA in My Blood?

A low fetal fraction can result from several circumstances, including gestational age, mother weight, and specific medical disorders. A reduced fetal percentage may result from the mother’s blood circulation containing less fetal DNA in the early stages of pregnancy. Furthermore, the fetal fraction may be impacted by obesity in the mother or specific difficulties such as placental problems or fetal anomalies.

What Causes Low Fetal Fraction?

An inadequate fetal fraction can result from several circumstances, such as:

• Early pregnancy period: A smaller fetal fraction is often produced in the initial stages of gestation when there is a generally smaller quantity of DNA from the fetus in the woman’s circulation.

• Obesity in mothers: Reduced fetal fraction levels have been linked to elevated maternal body mass indexes (BMI).

• Issues related to the placenta: A decreased fetal fraction may result from placental anomalies or difficulties that affect the release of fetal DNA into the mother’s bloodstream, such as placental mosaicism or limited placental mosaicism.

• Fetal anomalies: Fetal chromosomal disorders, such as trisomy or monosomies, can occasionally have an impact on the levels of the fetal fraction.
• Mother age: Research has found a correlation between higher mother age and lower fetal fraction levels.

• Ethnicity: While more research is required in this area, several studies have revealed that particular cultural backgrounds may be related to lower levels of fetal fraction.

What Does Fetal Sex Mean?

Within the framework of non-invasive prenatal testing, “fetal sex” denotes the biological gender of the growing fetus, as ascertained by examining the Y chromosome’s existence or lack in the fetal DNA specimen. Parents-to-be who want to find out their unborn child’s sex early in their pregnancies may find this helpful material.

Conclusion

The fetal fraction significantly influences the accuracy and dependability of NIPT testing. Expectant parents can more effectively interpret their NIPT results and make knowledgeable decisions regarding their prenatal care if they know this parameter’s relevance and the variables that may affect it. At Face DNA Test, we place a high value on giving our customers thorough and precise information so they may fully comprehend the most recent developments in fetal genetic testing. Our team of professionals is committed to helping you navigate NIPT’s complexities and ensuring you receive the information and assistance you require during your pregnancy journey.

FAQ

Can the NIPT Test Detect Miscarriage?

Although determining fetal sex and screening for chromosomal disorders are the main goals of NIPT, recent research has indicated that the test can additionally offer information about the risk of miscarriage or other pregnancy issues. However, additional study is required to support the application of NIPT in these contexts.