- Design
- Secondary analysis of a multicentre stepped-wedge cluster randomised trial
- Population
- 2,919 high-risk singleton pregnancies on low-dose aspirin, 18 units in Asia
- Primary outcome
- Preterm pre-eclampsia
- Effect
- 3.7% developed it; risk 1:2-1:5 vs 1:51-1:100 aOR 15.8 (8.2-30.7)
This secondary analysis drew on a stepped-wedge cluster randomised trial across 18 units in 10 Asian regions (2019 to 2022). It followed 2,919 women with singleton pregnancies screened high risk (1 in 100 or higher) by the first-trimester Fetal Medicine Foundation triple test, all taking low-dose aspirin. 280 (9.6%) developed pre-eclampsia and 107 (3.7%) developed it preterm.
Three features marked residual risk. Chronic hypertension (adjusted OR 1.84, 1.07 to 3.15) and a mean arterial pressure above 1.149 multiples of the median (adjusted OR 2.16, 1.43 to 3.26) were each associated with preterm disease. The estimated risk itself mattered most: compared with women at 1 in 51 to 1 in 100, those at 1 in 2 to 1 in 5 had about 16 times the odds (adjusted OR 15.8, 8.2 to 30.7), and those at 1 in 6 to 1 in 10 about eight times.
The practical message is that aspirin is not the end of the plan for the highest-risk women. Their screening number is worth reading as a measure of how closely to watch, not just a yes or no for aspirin. The study is relevant to South Asian practice, where FMF-based screening is spreading and chronic hypertension in pregnancy is common.
- Record the actual first-trimester risk figure in the notes, not only 'high risk'.
- Consider closer blood pressure and growth surveillance when the estimate is 1 in 10 or higher despite aspirin.
- Treat chronic hypertension plus a high screening risk as the group most likely to deliver early with pre-eclampsia.
- Check aspirin adherence and dose at each visit; residual risk is higher still if tablets are missed.
Why it matters
Starting aspirin is often treated as the whole response to a high screening result, and it is not.
Don't overread it
These are associations within a treated cohort; they do not show that any extra intervention lowers the residual risk.
The statistics, in plain English
The wide interval around the 16-fold figure (8 to 31) reflects small numbers in the highest-risk group, but even the lower end is a large effect. The 1 in 21 to 1 in 50 group's interval crossed 1, so it did not differ clearly from the reference.
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