What is faest (Fetus and Embryo Screening Test)?

Faest is a Non-Invasive Prenatal Screening (NIPS) test, based on Next-Generation Sequencing (NGS) analysis of the cell-free fetal DNA (cffDNA) from peripheral blood of a pregnant woman. faest detect fetal aneuploidy (extra number or a loss of fetal chromosomes).

Basis of faest

Each cell of a human body (except germ cells such as oocytes or sperm cells) have 46 chromosomes, 23 inherited from each parent. If there is

an extra copy of a chromosome present in the particular cell nuclei instead of the normal two, it causes developmental abnormalities. It is called a trisomy. Fetal trisomy in chromosome 21, 18, or 13 can lead to a viable birth with each of the trisomy called Down syndrome, Edwards syndrome, and Patau syndrome, respectively.

When the faest test is positive for an aneuploidy, additional diagnostic tests such as amniocentesis or CVS should be performed after consultation with doctors. The purpose of the faest is to decrease the number of cases which needs further invasive diagnostic tests due to the inaccurate indication of high risk from general serum-based screening

Advantages of faest

  • Require only a maternal blood sample instead of invasive collection of fetal samples with needle biopsies such as amniocentesis or Chorionic Villus Sampling (CVS).
  • Furthermore, since it is based on one of the most advanced DNA analysis technologies (NGS), it provides test results that are more accurate (>99%) than previous serum-based fetal screening tests.
  • faest is developed by Macrogen that provides higher accuracy and reliability than those of other NIPS tests from Korea since it has been validated with the largest number of aneuploidy-positive samples as well as samples collected from the earliest stages of gestation in Korea.
  • It is possible to get the test as early as at 10 weeks of gestation.
  • The test failure rate is less than 0.1%.
  • The faest is an excellent choice if your general serum screening indicated high risk for fetal chromosome abnormalities, or if you have a family history for fetal aneuploidy or a previous pregnancy with fetal aneuploidy

Sensitivity and Specificity of faest


Trisomy 21

Trisomy 18

Trisomy 13


(32 of 32)

(21 of 21)

(3 of 3)


(678 of 679)

(682 of 690)

(707 of 708)

Sensitivity: The probability of positive result from the positive specimens.

Specificity: The probability of negative result from the negative specimens.

Positive(+) : Chromosomal abnormality, Negative(-): Normal

Test Targets

  • Pregnant women who should be offered the faest test.
  • Pregnant women with the age of over 35.
  • High-risk group determined by serum-based screening tests.
  • Pregnant women with previous history of Down syndrome, Edwards syndrome or Patau Syndrome fetuses.
  • Pregnant women who want to avoid invasive amniocentesis or CVS.
  • Pregnant women who just want to get the test for herself as well as for her fetus.
  • 1- Consultation with obstetrics and gynecology specialists.
  • 2- Filling in the test request form as well as the informed consent form of the faest test.
  • 3- Drawing about 10 ml of blood at obstetrics and gynecology clinics.
  • 4- The blood will be transferred to Macrogen.
  • 5- Analyzeing fetal DNA in the blood. Delivery of the results to the clinics.