Fetal assessment, prenatal screening and counselling — branching viva

Station opening

Examiner: "The cell-free DNA screen is positive for trisomy 21. What do you tell the patient?" [1]

Strong candidate (must-hit)

• A positive screen is not a confirmed diagnosis; it raises probability and warrants counselling and an offer of diagnostic testing. [1] [16]
• Names chorionic villus sampling or amniocentesis as diagnostic options, gated by gestation, with contemporary procedure-related risk. [11]
• Counsels non-directively, offers written information and time, and does not push a decision in the same breath as the result. [18]
• Names the next step and a named owner before the patient leaves. [18]

Weak candidate

• "Your baby has Down syndrome." [1]
• Quoting a high legacy procedure-related loss rate to deter diagnostic testing. [11]

Branch A — Why pre-test probability matters

Examiner: "Does this positive result mean the same thing in a 19-year-old and a 41-year-old?" [1]

Strong

• No. Positive predictive value depends on pre-test probability, which rises with maternal age and other factors. [1] [16]
• States that the same screen-positive result carries a different chance of a true fetus in the two patients. [1]
• Uses pre-test probability to frame counselling and the offer of diagnostic testing. [16]

Weak

• "A positive is a positive; it means Down syndrome regardless." [1]
• Conflates screen sensitivity with positive predictive value. [16]

Branch B — The no-call result

Examiner: "A different patient has a no-call cell-free DNA result. Is she low-risk?" [1]

Strong

• No. A no-call is its own result state and carries increased risk of aneuploidy and fetal growth restriction. [1] [16]
• Options are repeat cell-free DNA, diagnostic testing or detailed ultrasound with surveillance, chosen by risk. [1]
• Does not relabel the no-call as a pass or a low-risk result. [16]

Weak

• "They couldn't run the test, so she is fine." [1]
• "Just repeat the test and if it is normal she is clear." [16]

Branch C — Soft marker reasoning

Examiner: "The anatomy scan shows an isolated echogenic intracardiac focus. What now?" [6]

Strong

• Reads the soft marker against the prior screen, not in isolation. [6]
• In a reassuringly screened pregnancy, an isolated soft marker usually changes nothing; in an unscreened pregnancy it recalculates risk. [6]
• Uses the SMFM framework for clinically significant isolated markers. [6]

Weak

• "An echogenic focus means the baby is at high risk of aneuploidy." [6]
• Ignoring the prior screening result entirely. [6]

Branch D — Abnormal Doppler and delivery timing

Examiner: "At 29 weeks the fetus is below the third centile with absent end-diastolic flow. What is the plan?" [8]

Strong

• Classifies as early-onset placental fetal growth restriction; Doppler drives surveillance and delivery timing. [8] [9]
• Intensifies Doppler surveillance, considers admission, and balances prematurity against intrauterine compromise when timing delivery. [8]
• Gives antenatal corticosteroids for fetal lung maturation and, at very preterm gestations, magnesium sulfate for neuroprotection, gated by gestation. [8]
• Alerts the neonatal team and plans place and time of delivery with neonatal capability present. [18]

Weak

• "It is just a small baby; review in four weeks." [8]
• Discharging with no surveillance plan or neonatal alert. [9]

Branch E — The paediatrician's role

Examiner: "Trisomy 21 is confirmed. As the paediatrician, what is your antenatal role?" [18]

Strong

• Translates the diagnosis into a postnatal plan: neonatal team readiness, feeding and cardiac surveillance, and developmental follow-up. [17] [18]
• Holds the medical-home role through birth and beyond; coordinates genetics, cardiology and allied health. [17]
• Counsels the family about realistic outcomes and support without ableism. [18]

Weak

• "That is obstetrics; I will see the baby after birth." [18]
• Offering a single outcome narrative that ignores family values and support. [18]