In a postpartum woman, how many weeks should low‑dose (81 mg) aspirin be continued?

Duration of Low-Dose Aspirin in the Postpartum Period

Low-dose aspirin initiated for preeclampsia prevention should be continued daily until delivery and then discontinued immediately postpartum—it is not routinely continued into the postpartum period. 1, 2

Guideline-Based Recommendations on Duration

The American College of Obstetricians and Gynecologists explicitly recommends that low-dose aspirin be continued daily until delivery, not beyond. 1, 3, 2 This represents the consensus across multiple international guidelines from the USA, Canada, Ireland, New Zealand, and the UK. 1

Key Timing Points:

• Initiation: Start between 12-16 weeks of gestation (optimally before 16 weeks) 1, 3, 2
• Continuation: Daily through pregnancy until delivery 1, 3, 2
• Discontinuation: At delivery—aspirin is stopped postpartum 1, 2

Rationale for Stopping at Delivery

The mechanistic basis for aspirin prophylaxis is specific to pregnancy physiology:

• Aspirin targets defective placentation and abnormal spiral artery remodeling that occur during the first and early second trimester 1
• Once the placenta is delivered, the pathophysiologic substrate for preeclampsia is removed 1
• The anti-inflammatory and endothelial-protective effects are only relevant while the placenta is present 1

Important Clinical Pitfalls to Avoid

Common Misconception About Postpartum Continuation

Do not confuse pregnancy-related aspirin prophylaxis with long-term cardiovascular disease prevention. 1 The timing and indication for aspirin in preeclampsia prevention (restricted to the gestational period) differs fundamentally from its use for cardiovascular disease, where lifelong therapy may be appropriate. 1

Stopping Before Delivery

Avoid the common error of discontinuing aspirin at 36 weeks "just to be safe"—this removes protection during a high-risk period without evidence-based rationale. 1 Preeclampsia risk persists throughout pregnancy and even into the early postpartum period, with eclamptic seizures potentially developing for the first time after delivery. 1

Exception for Planned Cesarean Section

For scheduled cesarean delivery with neuraxial anesthesia, consider discontinuing aspirin 7-10 days before surgery to allow adequate platelet recovery. 4 Verify platelet count >75 × 10⁹/L immediately before spinal anesthesia. 4

Safety Profile Through Delivery

Low-dose aspirin (75-162 mg daily) does not increase risks of placental abruption, postpartum hemorrhage, fetal intracranial bleeding, or perinatal mortality when continued until delivery. 1, 4 This safety profile supports continuation through the delivery period without routine early discontinuation. 1

Special Populations Requiring Postpartum Anticoagulation

Antiphospholipid Syndrome

Women with antiphospholipid syndrome require a different approach: anticoagulation (low-molecular-weight heparin) should be continued for 6-12 weeks postpartum, though low-dose aspirin itself is typically discontinued at delivery. 1 This extended anticoagulation protects against thrombotic events in the high-risk postpartum period. 1

Summary Algorithm

1. High-risk woman identified → Start aspirin 100-150 mg daily at 12-16 weeks 1, 3, 2
2. Continue daily through pregnancy → No interruption until delivery 1, 3, 2
3. At delivery → Discontinue aspirin 1, 2
4. Postpartum → No routine continuation (0 weeks postpartum) 1, 2
5. Exception: APS patients continue LMWH (not aspirin) for 6-12 weeks postpartum 1