A blood sample between 14 and 22 weeks of pregnancy is tested for three hormones in the blood (the earliest time to screen for open neural tube defects is week 15). These are Alpha Feto Protein, Free Estriol, free bHCG. The stage of pregnancy is most realistically determined by ultrasound. The levels of the three hormones in the blood are compared with the MoM (Multiple of Median) values which is the average of the same hormone results of pregnant women at the same week.
The concentration of these three substances, age and race, smoking and/or alcohol use, history of miscarriage, family history of Down’s syndrome, etc. are mathematically formulated into a computerized analysis of the risk of birth and the result is given as a probability estimate.
Interpretation:In Down’s Syndrome pregnancies, AFP and uE3 levels tend to decrease, whereas free ß-hCG levels tend to increase. The AFP level is also used to identify increased risks of open spina bifida or anencephaly. The doctor should interpret it.
Sample: Arm venous blood. Nonfasting.
Working day: Everyday
Result Time: 2 days at 6 PM
