Table of Contents

## What is normal fetal DNA percentage?

Fetal fraction, the percentage of cell-free DNA (cfDNA) that is from fetal origin in maternal peripheral blood, is generally at the range of 3–30%, with an average of about 13% [4].

### What is a normal fetal fraction for NIPT?

All methods of NIPT require a minimum fetal fraction for accurate trisomy screening, commonly estimated at 4% (4).

**Is a fetal fraction of 6% good?**

The proportion derived from the placenta is known as the fetal fraction. When measured between 10 and 20 gestational weeks, the average fetal fraction in the maternal plasma is 10% to 15% but can range from under 3% to over 30%.

**What should fetal fraction be at 12 weeks?**

In Caucasian women, at 12 weeks’ gestation (CRL, 65 mm), the median fetal fraction decreased with maternal weight from 11.7% at 60 kg to 3.9% at 160 kg (Figure 2), and the estimated proportion with fetal fraction below 4% increased from 0.7% at 60 kg to 51.1% at 160 kg (Table 3).

## What should fetal fraction be at 13 weeks?

The median fetal fraction was 10.0% (interquartile range, 7.8–13.0%) and this decreased with maternal weight from 11.7% at 60 kg to 3.9% at 160 kg. The estimated proportion with fetal fraction below 4% increased with maternal weight from 0.7% at 60 kg to 7.1% at 100 kg and 51.1% at 160 kg.

### Is high fetal fraction good?

Ilona Goldfarb, MD, a specialist in the Maternal-Fetal Medicine (MFM) Program at Massachusetts General Hospital, and colleagues have demonstrated that women with a high FF in the first trimester are at an increased risk of delivering an infant with birth weight less than the fifth percentile.

**What is the average fetal fraction for cfDNA analysis?**

In order to analyze the placental cfDNA, there must be at least four percent fetal fraction. The average woman will have between 10 and 15 percent fetal fraction between 10 and 20 weeks gestation. Fetal fraction measuring less than three to four percent is considered unsuitable to obtain accurate test results. What Determines Fetal Fraction?

**What is the average percent of DNA shared between family members?**

Average Percent DNA Shared Between Relatives Relationship Average % DNA Shared Range Identical Twin 100% N/A Parent / Child 50% (but 47.5% for father-son relationsh N/A Full Sibling 50% 38% – 61% Grandparent / Grandchild Aunt / Uncle Ni 25% 17% – 34%

## How accurate is the cfDNA Test at 10 weeks?

In order to analyze the placental cfDNA, there must be at least four percent fetal fraction. The average woman will have between 10 and 15 percent fetal fraction between 10 and 20 weeks gestation. Fetal fraction measuring less than three to four percent is considered unsuitable to obtain accurate test results.

### What is a normal fetal fraction at 10 weeks?

The average woman will have between 10 and 15 percent fetal fraction between 10 and 20 weeks gestation. Fetal fraction measuring less than three to four percent is considered unsuitable to obtain accurate test results.