Overview of maternal serum screening for down syndrome

Abstract

This presentation will cover the principles of Down syndrome screening and the progress of screening from the use of age, second trimester and later first trimester screening tests. Refinements of first trimester screening will be discussed, including the timing of blood and ultrasound components, accreditation of sonologists, addition of nasal bone and ductus venosus to risk assessments and progress towards measuring precision and bias in ultrasound. The benefits and disadvantages of first and second trimester screening tests will be compared. Newer developments assessing risk of neural tube defects at first trimester including loss of intracranial translucency, caudal midbrain displacement and first trimester AFP will be covered. Screening programs can also assess risk for other chromosomal abnormalities such as Edward, Pataus and sex chromosomal anomalies. Prediction of other adverse outcomes such as preterm birth, low birth weight and pre-eclampsia have also been studied. Practical issues in a screening program, such as interferences and confounding factors are important to recognise and will be briefly discussed. The lecture will conclude with recognition that screening is an individual ethical choice. Pre-test information and counselling are important and the implications of the follow-up diagnostic tests should be understood.