Aspirin Dose Escalation for the Prevention of Recurrent Preterm Delivery Trial

Inclusion Criteria: * 14 years or older * Singleton gestation. Twin gestation reduced to a singleton, either spontaneously or therapeutically, is not eligible unless the reduction occurred before 13 weeks 6 days project gestational age. Higher-order multifetal gestations reduced to singletons are not eligible. * Gestational age at randomization between 10 weeks 0 days and 15 weeks 6 days based on clinical information and evaluation of the earliest ultrasound. * Prior preterm birth between 20 weeks 0 days and 34 weeks 6 days with one of the following in the proximal birth reaching 20 weeks or greater: * Spontaneous preterm birth is defined as spontaneous preterm labor or premature rupture of membranes * Ischemic placental disease is defined as preeclampsia, small for gestational age, fetal growth restriction, or placental abruption, as defined clinically. * Stillbirth excluding those with known genetic disorders or major congenital anomalies. Exclusion Criteria: * Known allergy or hypersensitivity to aspirin or any medical condition where aspirin is contraindicated (e.g., history of peptic ulcer disease, nasal polyps, NSAID-induced asthma, history of gastrointestinal bleeding, known G6PD deficiency, severe hepatic dysfunction, bleeding disorders, and consumption of 3 or more alcoholic drinks per day) * Taking other anticoagulants such as Heparin or Low-Molecular weight Heparin * Thrombocytopenia defined as a platelet count defined as a platelet count \<100,000 microl…