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Sir,

It was pleasing to see that this RCT appears to show that low dose aspirin can reduce the incidence of pre-eclampsia in what certainly appeared to be a high risk group1. Although the 95% confidence intervals were extremely wide, these findings are consistent with a recent meta-analysis of trials using aspirin to prevent pre-eclampsia following uterine artery Doppler studies in the second trimester2. However, the authors have not presented convincing evidence that using bilateral ‘notching’ of the uterine arteries at 12–14 weeks is a useful screening test for predicting pre-eclampsia. The reference they cite was an observational study performed on 626 women between 12 and 16 weeks without any stratification for gestation3. A detailed analysis of the results from this cohort was published in the BJOG4. Thirty-three percent of these women had bilateral ‘notched’ uterine artery Doppler waveforms and 13% of these went on to develop pre-eclampsia. However, the authors identified changes in the waveform across the gestational age studied, with more ‘notching’ seen at earlier gestation. They also felt that the tests' usefulness was limited by its poor specificity and highlighted the need for prospective studies to reproduce their results. A larger and more recent study of 3324 ‘low risk’ women at 11–14 weeks demonstrated bilateral ‘notching’ in 55% and concluded that this was ‘unlikely to be useful in screening for pregnancy complications’5. We are not given outcome data for the 30 women (25%) who did not have bilateral ‘notching’ in the current study, but I would be surprised if they were statistically different to those 43 women who received placebo. I would therefore suggest that the current study provides further evidence for the use of low dose aspirin in preventing pre-eclampsia in a high risk group, but does not support the use of uterine artery ‘notching’ at 12–14 weeks in selecting these patients.

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