The triple screen during pregnancy is a blood test carried out during the second trimester (weeks 15 – 20) to signal if there is a risk of chromosomal abnormalities.  It is important to remember that the blood alone is not the only indicator used.  A woman’s age, ethnicity and other factors are combined with the bloodwork in order to estimate the chances that the fetus may have an abnormality.  These tests DO NOT diagnose a problem; they only indicate that further testing should be done.