The results showed that screening performance in the first trimester of pregnancy was virtually the same as that in the second trimester, and in either it was much less effective than integrating screening measurements from both trimesters into a single test. In applying these results to screening practice several conclusions can be drawn. The following tests offer the most effective and safe method of screening:
- overall: the integrated test
- if an NT measurement is not available: the serum integrated test
- for women who do not attend for antenatal care until the second trimester of pregnancy: the quadruple test
- for women who choose to have a screening test in the first trimester: the combined test.
At a constant detection rate, the cost-effectiveness of these four tests is broadly similar, any extra screening costs tending to be offset by fewer diagnostic costs. The evidence presented in this report does not support retaining the double test, the triple test, or NT measurements on their own (with or without maternal age) because each would lead to many more women having invasive diagnostic tests, without increasing the proportion of Downs syndrome pregnancies detected.