Single Best Answer (SBA) · Routine Antenatal Care
A woman books late at 16 weeks and her nuchal translucency cannot be measured. She still wishes to be screened for Down syndrome. Which single screening test is the strategy of choice in this situation?
Show answer and explanation
Answer: B. Quadruple test (second-trimester maternal serum screening)
Down screening when booking late
Down syndrome screening is recommended for all women, but the appropriate test depends on gestation and whether nuchal translucency can be measured.
Options
| Test | Components | Window |
|---|---|---|
| Combined first-trimester (CFTS) | NT + hCG + PAPP-A | NT 11+2 to 14+1 weeks |
| Quadruple test (2TMSS) | hCG, AFP, unconjugated oestriol, inhibin A | 14+2 to 20+0 weeks (best 15-17) |
This scenario
- The quadruple test is the screening strategy of choice in the second trimester for women booking later in pregnancy or when it is not possible to measure the NT.
- It uses maternal serum markers only and so does not depend on an early NT scan.
A high-risk result still leads to an offer of a diagnostic test (amniocentesis for karyotype).
Practise every Obstetrics & Gynaecology topic
This is a free sample. Sign up for the full bank of flashcards and exam-style questions on a spaced-repetition schedule, with 20 free stars a day.