First trimester screening refers to the prenatal screening test, which helps in early detection of an abnormality in the unborn fetus. Some of the abnormalities, which can emerge in an unborn fetus are genetic or chromosomal disorders like Down’s Syndrome (trisomy 21) and Edwards Syndrome (trisomy 18). The screening also helps to understand the profile of the growing baby. The First trimester screening test includes the following steps:
- Blood test – It is done to evaluate the Human chorionic gonadotropin (hCG) and Pregnancy-associated Plasma Protein-A (PAPP-A), which are pregnancy- determined substances, in the expectant woman’s blood
- Ultrasound scan – It is done to examine the amount of clear space or area in the tissue located at the back of the neck of the fetus (nuchal translucency). In addition, a full pelvic scanning is also done.
First trimester screening test is advised between 11th and 14th week of pregnancy. By assessing the age of the expectant woman and the results of both the blood test and ultrasound scan, the doctor can diagnose if the unborn fetus has any chromosomal abnormality. This helps the family to decide on whether to continue with the pregnancy or terminate it.
If the risk level investigated is low, this screening test can provide early comfort and reassurance of a fit and healthy pregnancy.
If the risk level investigated is moderate to high, then the woman might go for some other definitive tests.