The blood taken during the Down’s syndrome screening is the venous blood of the pregnant woman. When drawing venous blood from a pregnant woman, the appropriate puncture site is chosen based on the distribution and course of the veins on the body surface. The veins in the elbow joint, the back of the hand, and the wrist joint are usually the preferred sites for puncture. The specific site of the puncture does not affect the accuracy of the test results as long as the procedure is smooth. After the blood is drawn, the blood levels of human chorionic gonadotropin, alpha-fetoprotein and free estriol are measured. The results of these tests are combined with the mother’s age, weight, height and gestational age to assess the risk of Down’s syndrome in the fetus. At the time of Down’s syndrome screening, pregnant women should avoid catching a cold.