Discussion
PTD, pre-eclampsia
PRE-ECLAMPSIA, SECONDARY
In the present study, we aimed to assess the preventive effect of low-dose aspirin on PTL in pregnant women with a history of PTD. Although not being statistically significant, the findings of the present pilot study revealed that low-dose aspirin prescription in women with a history of PTD reduced the incidence of PTD. Moreover, we realized that in patients with a history of spontaneous PTD, receiving low-dose aspirin significantly reduced PTD if the patient experienced spontaneous labor in the current pregnancy.
In a study by Hoffman et al. on pregnant women from low- to middle-income countries, low-dose aspiring showed reduced PTD prior to 37 weeks, in addition to decreased perinatal mortality.

In studies investigating low-dose aspirin to prevent pre-eclampsia, a decrease in PTL is also reported. Nevertheless, the cause of PTL has not been reported generally, and apparently, a decrease in PTL could be due to the decrease in the incidence of pre-eclampsia as one of the important causes of PTL.
The results of the aforementioned studies suggest that, in some cases, low-dose aspirin may be effective in preventing spontaneous PTL, although those studies were secondary analyzes in women with risk factors for pre-eclampsia. Although our study, an independent study on women at risk for PTL, was associated with a reduced incidence of PTD in the aspirin group, there was no statistically significant difference. On the other hand, the median duration of prolongation of pregnancy was significantly higher in patients receiving tocolytic agents in the aspirin group. However, because the incidence of PTD was significantly lower in the aspirin group in a subgroup of patients who presented with spontaneous labor in the current pregnancy and were at risk for PTD, it may not be significant in all patients due to the small sample size.
No independent study has been conducted to investigate the effect of low-dose aspirin on the prevention of spontaneous PTL, and studies in this field have been the secondary analyses of research conducted on women with risk factors for pre-eclampsia. The latest recommendations of the American Association of Obstetricians and Gynecologists also indicate that currently, due to lack of sufficient evidence, prophylactic administration of low-dose aspirin has not been approved for the prevention of conditions such as PTL and stillbirth, among others, in the absence of risk factors for pre-eclampsia.
However, the small sample size, which was the most significant limitation of our study, may have provided statistically insignificant results. In addition, due to not using a placebo in our research, there was no blinding. Therefore, it is recommended to conduct extensive multicenter studies with larger sample sizes and utilize a placebo.
Despite our effort to provide a rationale for using low-dose aspirin in PTL, there were some limitations to the present study. The main limiting factor in the present study is the small sample size, eclipsing its representativeness. Further studies are needed to evaluate the effectiveness of low-dose aspirin in larger populations. Besides, as we were concerned about the term “proven therapy” as defined in the Helsinki declaration, we refused to expose patients in the control group to placebo drugs.
