Quadruple test refers to an antenatal screening test that aims to detect risk of trisomy 21. The test is done in second trimester usually between 14 to 20 weeks. This screen consists of 4 tests. These are highlighted below: - alpha fetoprotein - beta-hCG - inhibin A - unconjugated estradiol Reference: https://www.emmasdiary.co.uk/pregnancy-and-birth/2nd-trimester-pregnancy/tests-and-scans/the-quadruple-test Image via: https://ssl.adam.com/content.aspx?productid=617&pid=1&gid=007311&site=makatimed.adam.com&login=MAKA1603