From the Guidelines
The highest duration of thrombotic (blood clot) risk during pregnancy is from the first trimester to the postpartum period, with the greatest risk in the postpartum phase.
Key Points
- The risk of venous thromboembolism (VTE) is increased 4-fold to 6-fold during pregnancy, with the greatest risk in the post-partum phase 1.
- Pregnancy leads to all factors associated with the development of thrombosis, including hypercoagulability, stasis, and vascular injury, which start from conception and may not revert to normal until beyond 6 weeks postpartum 1.
- The incidence of VTE in the postpartum period is five times higher compared with antenatal, with a rate of 511.2 per 100,000 compared to 95.8 per 100,000 in the antenatal period 1.
- The risk of VTE is greater after surgical termination of pregnancy (STOP) compared to nonpregnant women, with a hazard ratio of 2.23 1.
- The risk of VTE after early pregnancy loss is lower than the first trimester VTE risk in all pregnancies, with a rate of 1.3 per 10,000 compared to 7.8 per 10,000 for term pregnancies 1.
Risk Factors
- Preexisting risk factors such as personal or family history of VTE, thrombophilia, medical comorbidities, age > 35, and BMI > 30 1.
- Obstetric risk factors such as multiple pregnancy, current preeclampsia, cesarean section, labor >24 hours, stillbirth, preterm birth, and postpartum hemorrhage 1.
- Transient risk factors such as hyperemesis, dehydration, immobility, current systemic infection, and any surgical procedure except perineal repair 1.
From the Research
Thrombotic Risk During Pregnancy
The risk of thrombotic events, such as venous thromboembolism (VTE), increases during pregnancy and the postpartum period 2, 3, 4, 5, 6.
Highest Duration of Thrombotic Risk
- The highest risk period for VTE is during the postpartum period, particularly in the first 3 weeks after delivery 5, 6.
- The incidence proportion of postpartum VTE is highest during the first week after delivery, with a rate of 9 per 10,000 deliveries, and decreases steadily through the 12th week 6.
- The risk of VTE remains elevated throughout the first 12 weeks after delivery, especially for women with obstetric complications such as cesarean delivery, preeclampsia, hemorrhage, and postpartum infection 6.
Risk Factors
- Pregnancy itself is a risk factor for VTE, with a fivefold increased risk compared to non-pregnant women of similar age 3, 4.
- Other risk factors include thrombophilia, cesarean delivery, postpartum infection, and the combination of obesity with immobilization 2.
- Women with previous VTE have an approximately 3.5-fold increased risk of recurrent VTE during pregnancy compared to non-pregnant periods 4.