Introduction
The prevalence of twin pregnancy is increasing, primarily as a result of the use of Assisted Reproductive Technologies (ART). Relative to singletons, twin pregnancies are associated with increased maternal and perinatal mortality and morbidity, the associated perinatal adverse outcomes, including preeclampsia (PE), small for gestational age (SGA) babies, and preterm birth (PTB).1 Recently, it has been reiterated that the incidence of PE in twin pregnancies is 3-4 times folds higher compared to singletons.2 A clinical cohort study containing 321 twin pregnancies demonstrated the incidence of at least one twin with birthweight <10thcentile was 47%, while at least one with birthweight <5th centile was 27%.3 It is also reported that the percentage of PTB in twin pregnancies is significantly higher than singletons, with 50-60% delivering prior to 37 weeks.4 The increasing morbidity and mortality associated with adverse pregnancy outcomes of PTB, PE, and SGA remain major concerns internationally. Although the etiology of these complications has yet been fully elucidated, their development is generally associated with increased inflammation and/or hypoxia.5-8
The well-described anti-inflammatory and anti-coagulation properties of aspirin have made it an appealing target for preventing gestational hypertensive disorders, but the specific mechanism is still unclear.9 According to recent studies, we have a better understanding of the effects of aspirin on the prophylaxis of PE, PTB, and SGA.10-12 Based on current data, the American College of Obstetricians and Gynecologists (ACOG) recommends daily low-dose aspirin (81mg/day) in pregnancy to prevent adverse outcomes and while not increasing the risk of postpartum hemorrhage.13 But another meta-analysis14concluded that a dose of aspirin between 100-150mg was more beneficial, especially if initiated before 16 weeks. However, the optimal dose has not reached a consensus. Unlike in singletons, few studies have explored the potential beneficial (or otherwise) effects of aspirin in twin pregnancies. The ACOG-guideline recommended pregnant women to take aspirin based on circumstantial evidence – according to the incidence of PE was much higher in twin pregnancies.13 But there is a relative lack of direct evidence whether aspirin could reduce these adverse outcomes in twin pregnancies.
Given the limited data on twin pregnancies and the often conflicting results in singleton pregnancies, we undertook an observational cohort study based on real-world data. We aimed to explore the potential benefits of aspirin on twin pregnancies and provides a theoretical basis for further researches.