Antenatal fetal surveillance — structured SAQ (15 marks)

(a) Choice of modality (3 marks)

One mark for the modality, one for the justification, one for naming the alternative excluded. [1]

• Modified biophysical profile (NST plus amniotic fluid volume) is the appropriate modality for a hypertensive woman with a normally grown fetus — a high-risk pregnancy where the acute markers (CTG, BPP) are indicated.[1]
• Justification: the CTG and BPP read current acid-base status, which is what gestational hypertension puts at risk acutely; Doppler is reserved for fetal growth restriction, where it reads placental function.[1]
• Alternative excluded: umbilical artery Doppler is not the first choice here because her fetus is not (yet) growth-restricted; Doppler in a normally grown fetus does not add benefit.[1][2]

(b) Biophysical profile components and interpretation (4 marks)

One mark for the five components, one for the scoring, one for the score bands, one for the principle. [3]

• Five components: non-stress test, fetal movement, fetal tone, fetal breathing, amniotic fluid volume.[3]
• Scoring: each component scores 0 or 2; total out of 10.[3]
• Interpretation: 8 to 10 normal; 6 equivocal (repeat within 24 hours, consider delivery if term); under 6 abnormal (deliver if viable).[3]
• Principle: the biophysical variables are depressed progressively by hypoxia, with the acute variables lost first; a normal BPP correlates with a normal fetal pH.[3]

(c) Change with FGR and the Alfirevic evidence (4 marks)

One mark for the change, one for Doppler as the modality of choice, one for the Alfirevic finding, one for the interval. [2]

• The change: an EFW on the 5th centile is fetal growth restriction territory (under the Delphi contributory definition with an abnormal Doppler), and this moves surveillance from the modified BPP to umbilical artery Doppler as the primary modality.[2]
• Why Doppler: it reads placental resistance and function — the chronic process driving the growth restriction — whereas the CTG becomes abnormal only late.[2]
• Alfirevic Cochrane review: umbilical artery Doppler in high-risk pregnancy reduces perinatal death (RR 0.71, NNT 203), stillbirths, induction and caesarean.[2]
• Interval: at this Doppler severity, surveillance at least every two weeks (or sooner), because a normal Doppler today does not exclude deterioration before the next scan.[2]

(d) Absent end-diastolic flow (4 marks)

One mark for the significance, one for admission, one for corticosteroids and neonatology, one for delivery timing. [4]

• Absent end-diastolic flow is a high-risk finding indicating severe placental resistance with a sharply rising risk of stillbirth and fetal acidosis.[4]
• Admit for inpatient surveillance with Doppler (including ductus venosus), computerised CTG, and daily fetal monitoring.[4]
• Give antenatal corticosteroids for fetal lung maturity and involve neonatology for anticipated preterm and growth-restricted infant care.[4]
• Delivery timing: plan delivery around 32 to 34 weeks if stable, or earlier if the ductus venosus or computerised CTG deteriorate (TRUFFLE framework); caesarean is usual because the growth-restricted fetus tolerates labour poorly.[4]