Vainio et al. show that low dose aspirin significantly reduces the incidence of pregnancy-induced hypertension (especially proteinuric pre-eclampsia) in women considered to be at high risk, and the Editor, in his Choice, states that the ‘results are convincing’, implying perhaps that the findings are clinically relevant.
However, the definitions of hypertension and pre-eclampsia in the study are the textbook minimum, and the study barely shows even a trend in the direction of benefit to mother or baby in terms of the clinically relevant risks of hypertension or pre-eclampsia, such as severe hypertension, significantly preterm delivery or severe intrauterine growth retardation. There were no differences even in the number of induced deliveries, let alone caesarean sections between the aspirin and the placebo groups. The mean gestational age and birthweight at delivery were over 39 weeks and greater than 3500 g in the placebo group. The number of babies with birthweight less than 2500 g were 3/43 and 4/43 in the aspirin and placebo groups, respectively.
The authors do not report on the severity of hypertension in terms of how many women in each group required de novo anti-hypertensive medication in pregnancy (or an increase in pre-existing medication), nor do they report on the need for closer maternofetal monitoring or hospital admission.
The study shows differences that are statistically significant and academically interesting, but which do not appear to be quite clinically relevant, a picture very similar to that shown in the study by Chappell et al.1, which extolled the benefits of anti-oxidant supplementation (vitamins C and E) in the reduction of the incidence of pre-eclampsia in a high risk population.
Appropriately, Vainio et al. suggest that a larger, probably multicentre, trial would be required to assess the effect of aspirin on early-onset pre-eclampsia and intrauterine growth retardation, but the virtual absence of trends with regard to these endpoints in this study leaves room for scepticism.
It would appear that aspirin, and perhaps vitamins, can modify the clinical course of hypertensive disease and pre-eclampsia in pregnancy slightly, but it is premature to suggest that they are effective in reducing significantly the important causes of maternal and fetal morbidity and mortality.