How is first trimester screening performed?
Although the specific details of each procedure vary slightly, first trimester screening generally involves the following tests to be performed between the 10th and 14th weeks of pregnancy: • An ultrasound test, usually a transvaginal ultrasound (a small ultrasound transducer is inserted through the vagina), is performed to examine the fetus. • Blood is drawn from the mother’s vein and sent to the laboratory for analysis. First trimester screening is not 100 percent accurate. It is only a screening test to determine if there is an increased risk of the fetus having a birth defect. It also helps to identity those women who may need additional testing or monitoring during their pregnancy. There can be false-positive results – indicating a problem when the fetus is actually healthy, or false negative results – indicating a normal result when the fetus actually does have a health problem.
