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Aspirin for prevention of preeclampsia in women with abnormal uterine artery doppler


Clinical bottom line

Five small studies suggest that aspirin may help prevent preeclampsia in women with abnormal uterine artery doppler. Given the amount of evidence this is only very preliminary finding because altered results from just two women would make the result non-significant.


A Coomarasamy et al. Aspirin for prevention of preeclampsia in women with abnormal uterine artery doppler: a meta-analysis. Obstetrics & Gynecology 2001 98: 861-866.


Several databases, including Cochrane, were searched for randomised trials up to November 2000. Enquiries were also made about unpublished studies.

For inclusion the target population was women who had an abnormal uterine artery doppler assessment in the second trimester of pregnancy, with any definition of abnormality accepted. The therapeutic intervention was low dose aspirin (any definition) compared with placebo or no treatment. The primary outcome was the number of women developing proteinuric hypertension, and birth weight.


Five relevant articles were identified. Trial quality was reasonable, with more than 95% follow up. Three trials were double blind. The aspirin dose was 50 to 100 mg a day.

The results of the five trials are shown in Figure 1. Only one of the trials had itself a statistically significant reduction in preeclampsia with aspirin. Overall there were 25/251 cases with aspirin (10%) and 40/247 (16%) with control. The relative risk was 0.6 (0.4 to 0.96) and the NNT was 16 (8-300).

Figure 1: Trials of aspirin in abnormal uterine artery doppler

Women on aspirin had babies on average 82 grams heavier, but this was not statistically significant. No other outcomes looked for was statistically significant.


THis is interesting, but a long way from being overwhelming evidence, and certainly insufficient evidence on which to base treatment. For instance, the upper confidence interval of the relative risk (0.96) comes close to 1, and if it was above 1 we would say that the result was not statistically significant. If just two more women developed preeclampsia with aspirin, or two fewer with control, the result would not be statistically significant.