The purpose of this study is assess platelet phenotypes based on aspirin dosing in pregnant patients at risk for the development preeclampsia who are taking 81mg twice a day aspirin. Blood samples will be collected approximately 4 weeks after initiation of aspirin to evaluate the platelet phenotype during pregnancy in patients.

Inclusion Criteria:

• Pregnant people prior to 17 weeks
• Prenatal care at NYU Langone Health Obstetrics and Gynecology Associates
• Age 18-50 years
• Singleton viable gestation
• Pregnant patients at high risk of preeclampsia: Patients meeting USPSTF recommendation for aspirin prophylaxis for preeclampsia based on clinical risk factors.

Exclusion Criteria:

• Undergoing glucose challenge test (GCT) at time of blood draw
• Allergy or intolerance to aspirin
• Antithrombotic or antiplatelet therapy
• Anemia (hemoglobin <10 g/dl) or thrombocytopenia (platelet count <100,000), or thrombocytosis (platelet count >600,000)
• Known hemorrhagic diathesis
• Planned delivery outside of NYU

The de-identified participant data from the final research dataset will be shared upon reasonable request beginning 9 to 36 months after publication or as required by a condition of awards or supporting agreements, provided the requesting investigator executes a data use agreement with NYU Langone Health. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's Data Sharing Strategy Board (DSSB). Requests should be directed to: lucia.muzzarelli@nyulangone.org. The protocol and statistical analysis plan will be posted on Clinicaltrials.gov only as required by federal regulation or supporting awards and agreements.

Beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research.

The investigator who proposed to use the data will be granted access upon reasonable request. Requests should be directed to lucia.muzzarelli@nyulangone.org To gain access, data requestors will need to sign a data access agreement. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's DSSB.