Timeline for β-hCG Decline After Abortion
After a surgical or medical abortion, serum β-hCG typically declines by approximately 70% within 3 days, 91% by day 5, and 97-99% by 7-14 days, with complete normalization (< 5 mIU/mL) usually occurring within 4-6 weeks. 1, 2
Expected β-hCG Decline Pattern
Early Decline (Days 1-5)
- Day 3 post-abortion: Mean decline of 70% (range 37-99%) from baseline 1
- Day 5 post-abortion: Mean decline of 91% (range 68-98%) from baseline 1
- A decline of at least 48-66% within 24 hours indicates successful abortion completion 3
Week 1-2 Follow-up
- Days 7-9: Mean decline of 97% (range 92-99%) 1
- Days 10-11: Mean decline of 98.5% (range 95-99.6%) 1
- Days 12-14: Mean decline of 98.7% (range 87-99.9%) 1
- A 99% decrease in β-hCG is noted in 99% of women by 15-71 days post-abortion 2
Clinical Thresholds for Follow-up
- β-hCG < 900 IU/L at 14-21 days post-abortion effectively excludes ongoing pregnancy (100% sensitivity, 81.5% specificity) 4
- β-hCG < 1000 IU/L at 14-21 days provides 85.7% sensitivity and 83.5% specificity for excluding ongoing pregnancy 4
Factors Affecting Decline Rate
Initial β-hCG Level
- The rate of decline follows a quadratic pattern—higher initial β-hCG values decline more rapidly 5
- Initial β-hCG level does not affect the percentage decline after medical abortion through 63 days gestation 1
Gestational Age
- Mean gestational age does not significantly affect the rate of β-hCG decline after successful medical abortion 1, 4
- However, gestational age > 6 weeks is an independent risk factor for requiring uterine aspiration (OR 6.0) 4
Warning Signs of Incomplete or Failed Abortion
Abnormal Decline Patterns
- < 21% decline at 2 days or < 60% decline at 7 days suggests retained trophoblastic tissue or ectopic pregnancy 5
- < 48% decline within 24 hours is unlikely to represent complete abortion 3
- Patients with incomplete abortion show only 25% ± 19% decline in 24 hours, compared to 66% ± 8% with complete abortion 3
Ongoing Pregnancy Risk
- β-hCG ≥ 900 IU/L at 14-21 days requires further evaluation to exclude ongoing pregnancy 4
- The ongoing pregnancy rate after medical abortion is approximately 0.9% 4
Clinical Management Algorithm
Immediate Post-Abortion (Days 1-5)
- Obtain baseline β-hCG on day of abortion 1
- For patients requiring early confirmation (due to preference, logistics, or pregnancy of unknown location), repeat β-hCG on day 5 may be clinically useful 1
- Expected decline by day 5: ≥ 91% from baseline 1
Standard Follow-up (Days 7-14)
- Routine follow-up β-hCG at 7-14 days is the standard approach 1, 2
- Combine clinical examination with β-hCG determination to assess completeness 2
- Ultrasonography should be performed only when clinically indicated, not routinely 2
Extended Monitoring
- Continue monitoring until β-hCG reaches < 5 mIU/mL (non-pregnant level) 5
- This typically occurs within 4-6 weeks but may take longer depending on initial values 2
Critical Pitfalls to Avoid
- Do not rely on a single β-hCG value—serial measurements are essential to establish the decline pattern 1, 5
- Do not assume complete abortion based solely on clinical symptoms; β-hCG confirmation is necessary 2
- Do not use ultrasonography routinely for follow-up; reserve it for cases with abnormal β-hCG decline or clinical concerns 2
- Do not discharge patients with β-hCG ≥ 900 IU/L at 14-21 days without excluding ongoing pregnancy 4
Special Considerations
Molar Pregnancy Context
- After evacuation of hydatidiform mole, β-hCG should be monitored every 1-2 weeks until normalization, then monthly for 6 months 6
- Plateaued or rising β-hCG after molar evacuation indicates gestational trophoblastic neoplasia requiring chemotherapy 6
- β-hCG ≥ 20,000 IU/L at 4 weeks post-evacuation is an indication for chemotherapy due to perforation risk 6