Fetal assessment, prenatal screening and counselling — formative SAQs

SAQ 1 — No-call cell-free DNA result in a higher-risk pregnancy (20 marks, ~15 minutes)

A 37-year-old woman at 11 weeks gestation, body mass index 34, has a cell-free DNA screen that reports a no-call result due to low fetal fraction. She asks whether that means the baby is fine and no further testing is needed. She lives two hours from the nearest diagnostic service and has intermittent phone reception. [1] [16]

Questions

1. Define screening versus diagnostic testing and explain why this distinction matters now. (3 marks) [1]
2. Explain why a no-call cell-free DNA result is not equivalent to a low-risk result. (4 marks) [1] [16]
3. Outline the management options for a no-call result and the factors that guide the choice between repeat screen and diagnostic testing. (5 marks) [1] [11]
4. Give four elements of non-directive counselling you would use with this woman at this visit. (4 marks) [6] [18]
5. Describe four system actions that ensure she is not lost to follow-up given rural geography and access barriers. (4 marks) [18]

Model answer anchors

1. Screening estimates a probability of a condition; diagnostic testing confirms or excludes it. A no-call screen is neither, so the distinction determines whether to repeat, diagnose or surveil rather than reassure. [1]
2. A no-call reflects low fetal fraction, which is itself associated with raised maternal body mass index, early sampling, aneuploidy and fetal growth restriction; the no-call is therefore an informative signal carrying its own risk, not a low-risk result. [1] [16]
3. Options are repeat cell-free DNA, diagnostic testing (chorionic villus sampling or amniocentesis by gestation), and detailed ultrasound with surveillance. Higher pre-test probability favours diagnostic testing over simple repeat screen; quoted procedure-related risk should be contemporary. [1] [11] [12]
4. A no-call is not a normal result; what the next options are and their risks; that the choice is hers with support; clear written information; teach-back; named contact for questions. [6] [18]
5. Book before discharge; dual contact details and a backup number; interpreter if needed; transport and leave-from-work support; active chase list; written and verbal plan with a named owner. [18]