Is 150mg Aspirin Considered High Dose in Pregnancy?
No, 150mg aspirin is not considered high dose for pregnant women at risk of preeclampsia—it falls within the recommended low-dose range and is increasingly recognized as the optimal dose for preeclampsia prevention. 1, 2
Defining Low-Dose vs High-Dose Aspirin in Pregnancy
Low-dose aspirin in pregnancy is defined as 75-162 mg daily, with most international guidelines specifying a range of 75-150 mg. 1, 3 The term "high-dose" aspirin refers to doses exceeding 162 mg daily, which are associated with increased risks and are specifically warned against by the FDA in the third trimester. 2
International Guideline Dosing Recommendations
Multiple major guidelines explicitly endorse 150mg as an appropriate low-dose:
ISSHP (International Society for the Study of Hypertension in Pregnancy) recommends 75-162 mg daily, with 150 mg specifically mentioned for high-risk women identified through first-trimester screening. 1, 2
Royal College of Obstetricians and Gynaecologists (RCOG) recommends 150 mg daily as their standard dose. 4
International Federation of Gynecology and Obstetrics (FIGO) recommends 150 mg daily, noting that two 81mg tablets is an acceptable alternative. 1, 4
German guidelines specify 150 mg as their recommended dose. 1
Multiple European guidelines recommend dose ranges of 80-150 mg, 100-150 mg, or 75-150 mg. 1
Evidence Supporting 150mg as Optimal Dosing
Emerging evidence suggests that 150mg may be more effective than the traditional 81mg dose, particularly for certain high-risk populations:
Dose-Response Relationship
Meta-analyses demonstrate that aspirin doses ≥100 mg initiated before 16 weeks are significantly more effective than lower doses, with a risk reduction of RR 0.33 (95% CI 0.19-0.57, p<0.0001) for preeclampsia. 1
Head-to-Head Comparison Studies
A 2023 randomized controlled trial directly comparing 150mg versus 75mg aspirin found:
- Preeclampsia occurred in 8.77% of women taking 150mg versus 33.92% taking 75mg (p=0.001, OR=5.341). 5
- Similar fetomaternal safety outcomes between both doses. 5
A 2020 randomized trial showed:
- Preeclampsia occurred in 6.5% with 150mg versus 17% with 75mg (p<0.05). 6
- No significant differences in fetal outcomes between doses. 6
Special Populations Requiring Higher Dosing
Certain high-risk populations may particularly benefit from 150mg dosing rather than the standard 81mg:
Women with Chronic Hypertension
- Standard 81mg aspirin does not reduce superimposed preeclampsia in women with chronic hypertension (RR 0.97,95% CI 0.84-1.12, p=0.28). 1, 2
- FIGO specifically suggests considering 150-162mg for this population. 1, 2
Women with Diabetes
- The American Diabetes Association recommends 100-150 mg daily for pregnant women with type 1 or type 2 diabetes. 1, 2
Women with Obesity
- Women with BMI >40 kg/m² have higher thromboxane B2 levels and lower rates of complete platelet inhibition with 81mg aspirin. 1
- Higher doses may be needed to overcome altered pharmacokinetics in obesity. 1, 2
Safety Profile of 150mg Aspirin
150mg aspirin maintains the same excellent safety profile as 81mg, with no increased risks of:
- Placental abruption 2, 7, 8
- Postpartum hemorrhage 2, 7, 8
- Fetal intracranial bleeding 2, 7, 8
- Perinatal mortality 2, 7, 8
- Congenital anomalies 2, 7, 8
Clinical Implementation
For pregnant women at high risk of preeclampsia:
Initiate aspirin between 12-16 weeks of gestation (optimally before 16 weeks). 1, 2, 8, 3
Consider 150mg daily rather than 81mg, particularly for women with:
Continue daily until delivery (not stopping at 36 weeks). 1, 2
Common Pitfall to Avoid
Do not confuse 150mg with "high-dose" aspirin—this terminology error may lead to inappropriate withholding of optimal therapy. The FDA warnings about aspirin in pregnancy refer to doses >162mg, not the 150mg dose recommended by multiple international guidelines. 2