Table 3.

Effectiveness of aspirin on superimposed preeclampsia according to the time of drug ingestion

Author	Year	Population	Purpose	Design	Main findings	Risk of bias
Hermida, Ayala et al [4]	1999	240 pregnant women at risk of PE	To assess time-dependent effects of aspirin 100 mg in women at differing risk of PE	A double-blind, randomized, placebo-controlled trial	There was no effect of aspirin on the blood pressure of women who took aspirin on waking up. Aspirin significantly reduced blood pressure in those who took it 8 h after waking up. The effect was highly statistically significant among women who took aspirin before bedtime	Low
Ruan [62]	2011	1245 patients with hypertension	To assess the effect of the administration of low-dose aspirin before bedtime on blood pressure in hypertensive patients	A systematic review of 6 Randomized controlled clinical trials	Compared to aspirin on waking up, aspirin intake before bedtime had a significant effect on lowering SBP (mean difference: − 6.29 mmHg, 95%CI: (− 8.01, − 4.58)), and DBP (mean difference: − 2.26 mmHg, 95%CI: (− 4.95, 0.43)	Moderate
Xiao, Ling et al [77]	2023	266 pregnant women at high risk of PE	To assess the efficacy of aspirin 75 mg in high-risk pregnancies when taken at different times	Retrospective chart review	Aspirin taken at bedtime had a significantly lower incidence of PE than at other times. There was a higher occurrence of PE in those with chronic hypertension despite taking aspirin compared with those without hypertension (p = 0.0001)	Low
Sinha, Singh et al [68]	2023	116 women at high risk of preeclampsia	To compare the efficacy of 150 mg versus 75 mg aspirin in the prevention of preeclampsia among high-risk pregnancies	Parallel, open-label, randomized control trial	Aspirin 150 mg once a day at bedtime was more effective than 75 mg once a day at bedtime in preventing PE	Moderate