Is Down syndrome screening important?

Pregnancy check-ups are very important. Through prenatal check-ups, you can determine whether the baby is healthy, whether it is fully developed in the belly, and whether you can give birth to a healthy child. There are many types of pregnancy check-ups, such as measuring the fetal height, fetal weight, fetal blood type, electrocardiogram, etc., which can observe whether the baby is developing healthily in the belly. Is Down syndrome screening really important? This is a question that many people are concerned about.

During the Down syndrome screening, expectant mothers will also have their AFP, HCG, uE3, and Inhibin A checked in their serum. These tests can help detect whether the fetus suffers from NTD [neural tube defect], 18-trisomy, and 13-trisomy syndrome. Expectant mothers should go to the hospital for prenatal check-up to have blood drawn for Down syndrome screening one week before each prenatal check-up. The results will be available when they go to the hospital for prenatal check-up one week later. If the serum screening result is positive, then chorionic villus biopsy and amniotic fluid puncture will be needed to confirm whether the pregnant woman is pregnant with Down syndrome.

Expectant mothers should go to bed early the day before the Down syndrome screening, and should not drink water from midnight. They should not eat on the morning of the examination and should go directly to the hospital for the examination on an empty stomach. Before the examination, the doctor will ask the expectant mother about her menstrual period, weight, gestational age, height, etc. The expectant mother must tell the doctor truthfully after arriving at the hospital.

Down syndrome screening mainly includes the following tests. Generally, only four samples need to be drawn for testing to get the results: venous blood drawing, ultrasound examination of the thickness of the translucent membrane on the back of the expectant mother's neck, ultrasound examination of AFP [alpha-fetoprotein], HCG [human chorionic gonadotropin], uE3 [free estriol], and Inhibin A [inhibin A]. Doctors check the indicators of these items and combine them with the expectant mother's menstrual period, weight, gestational age, height, etc. to determine the probability of a pregnant woman having a baby with Down syndrome. The accuracy of the examination is extremely high.

Currently, there are two main methods for Down syndrome screening in clinical practice. One is prenatal screening, and the other is non-invasive DNA testing.

【Antenatal screening】

Prenatal screening refers to screening by checking various indicators in the serum of expectant mothers. The main methods include radioimmunoassay, enzyme immunoassay, chemiluminescence and time-resolved immunofluorescence. The test results of radioimmunoassay and enzyme immunoassay are prone to variation. In order to ensure the accuracy of the test results, these two methods are rarely used now.

【Non-invasive DNA testing】

Since 2010, non-invasive DNA testing has been introduced in clinical practice. The principle of this method is very simple. The fetus absorbs nutrients from the expectant mother's body and releases waste through the placenta. At the same time, part of the cell fluid will penetrate into the expectant mother's blood through the placenta. When the expectant mother's immune system encounters the blood that infiltrates the fetus, it will initiate an immune response and destroy the blood that has infiltrated into her own blood, but the fetus's DNA will remain. At this time, only 5 ml of blood needs to be drawn from the expectant mother to accurately detect whether the fetus's DNA is normal.

Experts point out that the results of Down syndrome screening are most accurate when pregnant women undergo it between the fourth and fifth months of pregnancy. It is better for expectant mothers to do the screening in advance and have a doctor who can help with the prenatal check-up. Currently, Down syndrome screening cannot 100% prove that a baby with Down syndrome is being pregnant, so many expectant mothers will question Down syndrome screening. However, Down syndrome screening is the easiest way to detect whether a baby with Down syndrome is being pregnant, and the fetus will not be harmed during the examination. Only if the results of the serum test are suspicious will further amniocentesis be needed to confirm the diagnosis.