First trimester, second trimester, integrated or sequential genetic screenings are all variations of the same detection strategy for trisomies 13, 18, 21 and neural tube defects. What you should know is that some of these conditions are lethal and some are associated with sever handicap. There is little to be done medically speaking to influence the course of such pregnancies but the most important aspect is to be informed and able to make decisions.
It is very important to understand that a screening test is a statistical tool based on comparison with other patients and it gives an estimate of probability for the disease. A positive screening test is a calculation on the paper and it always must be followed by a confirmatory test. However the diagnostic test is more invasive and carries a risk to which not everyone needs to be exposed.
The art is in the careful assessment of the balance of risk/benefit for each individual, which gives the possibility of making the most comfortable decision and we emphasize again on the way the information is presented to the patient. To eliminate the wrongful interpretations, the latest ACOG recommendations, to offer the confirmatory amniocentesis to any pregnant patient upon request, comes to reinforce our point.