Antiplatelet agents (mainly low-dose aspirin) have been shown to reduce the risk of preeclampsia in women at risk for the condition. The American College of Obstetricians and Gynecologists currently supports consideration of the use of low-dose aspirin (81 mg/day), initiated between 12 and 28 weeks of gestation, for the prevention of preeclampsia in women at high risk.1
Can antiplatelet agents also reduce the risk of preterm birth? It is a reasonable question, postulate van Vliet and colleagues2: Women with a history of preeclampsia also have an increased risk of spontaneous preterm birth (SPB), and vice versa. Uteroplacental ischemia is present in cases of preeclampsia, and research is showing that uteroplacental ischemia also plays a role in the etiology of spontaneous preterm labor.3,4
Details of the study
To investigate their research question, van Vliet and colleagues performed an additional analysis of the Perinatal Antiplatelet Review of International Studies Individual Participant Data meta-analysis. The original meta-analysis involved the data of 32,217 women at risk for preeclampsia who were randomly assigned to low-dose aspirin-dipyridamole or placebo (no treatment); the study revealed a moderate risk reduction for preeclampsia as well as a significant reduction in preterm birth at less than 34 weeks of gestation in women treated with antiplatelets.2
In the additional analysis, for women with an SPB who began antiplatelet treatment before 20 weeks of gestation, the researchers assessed the time between 20 weeks and spontaneous preterm delivery, iatrogenic preterm delivery, and any preterm delivery. Overall, 9.7% of women (n = 2,670) had an SPB before 37 weeks of gestation, 2.8% (n = 773) had an SPB before 34 weeks of gestation, and 0.5% (n = 151) had an SPB before 28 weeks of gestation. Antiplatelet agents were associated with a significant reduction in the risk of SPB before 37 weeks (relative risk [RR], 0.93; 95% confidence interval [CI], 0.86–0.996) and before 34 weeks (RR, 0.86; 95% CI, 0.76–0.99). The RR of having an SPB at less than 37 weeks of gestation was 0.83 for women with a previous pregnancy and 0.98 for women in their first pregnancy.2
Antiplatelet use resulted in a 7% reduction in SPB risk in women at risk for preeclampsia. Antiplatelet use resulted in a 14% reduction in moderate to very preterm birth risk (<34 weeks’ gestation).
The authors advise that their study “provides clinicians with the best available evidence to counsel women regarding who might benefit from” antiplatelet use during pregnancy and suggest that antiplatelet use may be a promising intervention for women at high risk for SPB, especially in high-risk women with a previous pregnancy.2
The researchers found no difference among those receiving and not receiving antiplatelets in the incidence of antepartum hemorrhage (RR, 1.02; 95% CI, 0.90–1.15), placental abruption (RR, 1.13; 95% CI, 0.87–1.48), or neonatal bleeding (RR, 0.93; 95% CI, 0.80–1.09). The incidence of postpartum hemorrhage (PPH) was again found to be borderline significant (RR, 1.06; 95% CI, 1.00–1.13), but it was more frequent. The authors caution that the SPB reduction that they found in their study (as well as the reduced risk for preeclampsia with low-dose aspirin use) be balanced against the potential higher risk for PPH.2