Preeclampsia prediction and prevention — structured SAQ (15 marks)

(a) Risk assessment (4 marks)

One mark for naming the model, two for correctly identifying her factors, one for the decision. ^[3][8]

• Model used: the risk-factor checklist adopted by NICE, the USPSTF and ANZ practice — one high-risk factor, or two moderate-risk factors, triggers aspirin.^[3][8]
• High-risk factors present: previous hypertensive disease in pregnancy (preeclampsia at 31 weeks). That alone is sufficient.^[3]
• Moderate-risk factors present: age 40 years or more is not yet met at 39, but booking body mass index of 35 kg/m2 or more is present. Multiparity means nulliparity does not apply.^[3]
• Decision: she qualifies on a single high-risk factor, so she starts aspirin today. Her early-onset index disease also puts her at the higher end of recurrence risk — the pooled recurrence of preeclampsia is around one in five and rises the earlier and more severe the index episode.^[9][3]

(b) The preventive prescription (5 marks)

One mark each for: drug and dose; start gestation; stop gestation; calcium with its indication; the trial evidence. ^[1][2][7]

• ASPRE: 1,776 women at high risk by the competing-risks model, aspirin 150 mg nightly from 11 to 14 weeks until 36 weeks. Preterm preeclampsia fell from 4.3% to 1.6% (odds ratio 0.38, 95% CI 0.20 to 0.74; P = 0.004), with no significant excess of neonatal adverse events.^[1]
• Roberge dose-response meta-analysis: 45 trials, 20,909 women, doses 50 to 150 mg. Started at or before 16 weeks, aspirin reduced preeclampsia (RR 0.57), severe preeclampsia (RR 0.47) and fetal growth restriction (RR 0.56), each with a significant dose-response. Started after 16 weeks the effect on preeclampsia shrank to RR 0.81 with no dose-response, and there was no effect on severe preeclampsia or growth restriction.^[2]
• Calcium: the Cochrane review found high-dose calcium (1 g per day or more) may reduce preeclampsia and preterm birth, particularly with low-calcium diets, and reduces the composite of maternal death or serious morbidity, on low-quality evidence.^[7]
• State what you will not offer: bed rest, salt restriction, vitamins C and E, fish oil and garlic do not prevent preeclampsia.^[4][8]

(c) First-trimester combined screening (4 marks)

One mark for the four inputs, one for the gestational window, one for performance, one for the comparison with the checklist. ^[6][5]

• Window: 11 to 13+6 weeks, usually alongside the aneuploidy screen.^[6]
• Four inputs: maternal factors (age, weight, height, ethnicity, parity, obstetric and medical history, conception method); mean arterial pressure; uterine artery pulsatility index; and serum placental growth factor (PAPP-A as an alternative where placental growth factor is unavailable).^[6]
• Performance: O'Gorman reported detection of 75% of preterm preeclampsia and 47% of term preeclampsia at a 10% false-positive rate, with PAPP-A adding little once placental growth factor was included.^[6]
• Head-to-head: in SPREE (16,747 pregnancies) at a screen-positive rate of 10.3%, the NICE checklist detected 40.8% of preterm preeclampsia; maternal factors plus mean arterial pressure plus placental growth factor reached 69.0%; adding uterine artery pulsatility index reached 82.4%.^[5]
• The implementation caveat that earns the last mark: SPREE found compliance with the NICE recommendation to give first-trimester aspirin to high-risk women was only 23%. A better screen is worthless without the prescription.^[5]

(d) Counselling about residual risk (2 marks)

One mark for honesty about relative rather than absolute protection, one for the surveillance and safety-net message. ^[1][9]

• "Aspirin substantially reduces the chance of preeclampsia coming early, but it does not guarantee it will not happen. In the ASPRE trial the risk of preterm preeclampsia fell from about 4 in 100 to about 2 in 100 in women at high risk."^[1]
• "It has much less effect on preeclampsia at term, so we will still watch you closely: blood pressure and urine at every visit, growth scans, and a written list of symptoms that should bring you straight in."^[1][8]
• "If it does happen again, that will not be because you did anything wrong."^[9]