Sequential screening for chromosomal screening

What is Sequential screening:- A series of screening tests carried out during the course of the pregnancy. The background  or a priori risk depends on maternal age and gestation.  The individual patient-specific risk is calculated by multiplying the a priori risk with a series of likelihood ratios, which depend on the results of a series of screening tests carried out during the course of the pregnancy. Every time a test is carried out the a priori risk is multiplied by the likelihood ratio of the test to calculate a new risk, which then becomes the a priori risk for the next test.

What is NT scan ?? Nuchal translucency (NT) has emerged as the most sensitive ultrasound marker for detection of chromosomal anomalies in the first trimester. Nuchal translucency (NT) measurements are done between 11 -13.6 weeks of gestation.