The purpose of this research study is to evaluate the effect of low-dose aspirin on recovery from severe preeclampsia (a high blood pressure disorder of pregnancy) among women who have given birth. We hypothesize that taking aspirin for the first week after giving birth will enhance recovery from preeclampsia by decreasing the levels of a protein called soluble fms-like tyrosine kinase (sFlt-1), which is thought to be a main contributor to the development of preeclampsia, and speeding up return to a normal blood pressure.

Preeclampsia is a condition of the antenatal and postpartum periods, which manifests as new-onset hypertension and end-organ damage. Globally, preeclampsia is estimated to affect up to 9% of all pregnancies, though as many as two-thirds of patients who receive this diagnosis will remain hypertensive beyond the time of their postpartum hospital discharge. Because of this, postpartum preeclampsia is the leading cause of postpartum hospital readmission in the United States. Anti-hypertensive medications and magnesium sulfate are temporizing therapies aimed at preventing the immediate sequelae of preeclampsia such as seizures, stroke, and end-organ damage. However, there are no therapies directly targeting the pathophysiology underlying postpartum preeclampsia, which poses difficulties in promoting blood pressure recovery to a normotensive state.

Preeclampsia is considered a disorder of abnormal placentation, leading to the release of abnormal pro-angiogenic, anti-angiogenic, and vasoactive molecules. Specifically, excess elevations in anti-angiogenic proteins like soluble fms-like tyrosine kinase 1 (sFlt-1) relative to pro-angiogenic proteins like placental growth factor (PlGF) are thought to cause vasospasm and, in turn, hypertension. As such, it seems plausible that persistent postpartum sFlt-1 elevation is implicated in the pathophysiology of postpartum preeclampsia.

At low doses, acetylsalicylic acid, or aspirin, has been proven to target the aforementioned angiogenic imbalance by decreasing serum sFlt-1 levels. While aspirin is widely used during pregnancy to mitigate the risk of preeclampsia, the utility of aspirin in the postpartum period to target these pathways and promote BP recovery to a normotensive state is unknown. The central hypothesis of this trial is that use of aspirin in the first week postpartum will enhance recovery from preeclampsia by improving blood pressure recovery via decreased levels of sFlt-1.

Inclusion Criteria:

• Preeclampsia with severe features diagnosed during delivery admission, as defined by ACOG criteria.
• Pre- and postnatal care provided by the Long Beach Memorial Ob/Gyn resident or Maternal-Fetal Medicine clinic.

Exclusion Criteria:

• Patient age <18 years old
• Non-English or Non-Spanish speaking
• Chronic hypertension diagnosed before 20 weeks' gestation
• Known allergy, prior adverse reaction, or any medical condition in which aspirin is contraindicated (nasal polyps, gastric or duodenal ulcers, history of gastrointestinal bleeding, severe hepatic dysfunction)
• Aspirin prescribed postpartum for any other medical condition
• Bleeding disorder
• Breastfeeding an infant with thrombocytopenia

The outcomes assessor will be blinded to study arms.