What are the Tri-Test and the Duo Test or Bi-Test
The Duo-Test or Bi-Test and the Tri-Test are part of the non-invasive prenatal diagnosis tests.
The Tri-Test is a simple blood test that is performed between the 15th and 18th week of pregnancy and during which 3 hormones are dosed: Beta HCG, estriol and alphafetoprotein (the latter is a substance that is produced by the liver and cells of the fetal intestine. It is found in the blood of the fetus, in the amniotic fluid and in the blood of the mother where it is detected in increasing quantities until the 32nd week and then decreases). This data is also associated with the age of the mother.
The Tri-Test is used to calculate the probability of having a child with Down Syndrome / Trisomy 21 (and only experimentally other trisomies).
This type of examination is probabilistic, that is, it is not used to make a precise diagnosis. Usually the Bi-test (or duo-test) is preferred to the Tri-test.
The Bi-Test
The Bi-Test is the dosage of PAPP-A and beta HCG.
PAPP-A (Pregnancy-Associated Protein A) is produced by the placenta from the 8th-9th week of gestation and is detected in maternal blood by normal blood sampling.
A low level of this protein increases the risk that the child will have Down syndrome.
The sampling done already in the first weeks of pregnancy (between 9 + 0 and 13 + 6 weeks of pregnancy) can highlight a greater or lesser risk of having a sick child.
Also in this case the results of nuchal translucency are associated with the bi-test, and other important parameters, including maternal age, for the calculation of the combined risk (we speak of Combined Test or Ultrascreen).
Kathryn Barlow is an OB/GYN doctor, which is the medical specialty that deals with the care of women's reproductive health, including pregnancy and childbirth.
Obstetricians provide care to women during pregnancy, labor, and delivery, while gynecologists focus on the health of the female reproductive system, including the ovaries, uterus, vagina, and breasts. OB/GYN doctors are trained to provide medical and surgical care for a wide range of conditions related to women's reproductive health.