Principles of first trimester screening in the age of non-invasive prenatal diagnosis: screening for other major defects and pregnancy complications.

<bold>Purpose: </bold>First trimester risk assessment plays a major role in the contemporary pregnancy care. It has evolved significantly since its introduction in the 1990s when it essentially consisted of just the nuchal translucency measurement. Today, it involves the measurement of several biophysical and biochemical markers and can assess the risk for a wide array of major chromosomal and non-chromosomal defects as well as other pregnancy-related complications.<bold>Methods: </bold>A search of the Medline and Embase databases was done looking for articles about first trimester screening. We performed a detailed review of the literature to evaluate the screening tests currently available and their respective test performance.<bold>Results: </bold>The detailed ultrasound examination results in the detection of about half of major structural defects, determination of a very accurate gestational age, and identification of multiple pregnancies as well as their chorionicity. In addition, risk assessment for preeclampsia and early IUGR can be established at this stage. In case of an increased risk, the daily use of low-dose aspirin can be offered at a point in pregnancy when it still can have a positive impact. Additional screening tests for gestational diabetes and macrosomia are available.<bold>Conclusion: </bold>Contemporary first trimester screening is essential to establish an individual risk profile and can be used to tailor the pregnancy care. [ABSTRACT FROM AUTHOR]