What is the recommended management for a patient with a history of one second trimester abortion in a previous pregnancy?

Management of Second Pregnancy Following Prior Second Trimester Loss

Serial ultrasound assessment of cervical length starting at 16 weeks with cerclage placement only if cervical shortening (<25mm) or funneling (>25%) is detected represents the optimal evidence-based approach for this patient. 1

Rationale for Serial Ultrasound Surveillance Over Prophylactic Cerclage

The most recent high-quality evidence demonstrates that serial transvaginal ultrasound monitoring with selective cerclage placement achieves equivalent outcomes to universal prophylactic cerclage, while avoiding unnecessary surgical intervention in approximately 64% of patients. 1

Key Evidence Supporting This Approach

• In patients with one prior second trimester loss, serial transvaginal ultrasound surveillance (starting at 14-16 weeks) with cerclage only when indicated by cervical changes showed no difference in preterm delivery rates compared to prophylactic cerclage at 13 weeks 1

• Preterm delivery <35 weeks occurred in 30% with ultrasound-guided management versus 23% with prophylactic cerclage (not statistically significant, P=0.3) 1

• Mean gestational age at delivery was identical between groups (34.4 vs 34.6 weeks) 1

• Only 36% of patients monitored with ultrasound ultimately required therapeutic cerclage, meaning prophylactic cerclage would have been unnecessary in nearly two-thirds of cases 1

Recommended Surveillance Protocol

Timing and Frequency

• Begin transvaginal ultrasound cervical length assessments at 16 weeks gestation 2

• Continue surveillance every 2 weeks until at least 24 weeks gestation 2

• More frequent monitoring (weekly) may be warranted if borderline cervical changes are detected 2

Intervention Thresholds

• Place therapeutic cerclage (McDonald technique) if cervical length measures <25mm before 24 weeks 1

• Place therapeutic cerclage if cervical funneling exceeds 25% of total cervical length before 24 weeks 1

• Cerclage placement should occur promptly once these thresholds are met, as delay may reduce effectiveness 2

Why Not Prophylactic Cerclage at 13 Weeks?

Prophylactic cerclage at 13 weeks exposes all patients to surgical risks when only approximately one-third will actually develop cervical insufficiency requiring intervention. 1

Risks of Unnecessary Cerclage

• Cervical trauma from the procedure itself 2

• Risk of membrane rupture (1-2% risk) 2

• Increased risk of preterm premature rupture of membranes 2

• Potential for ascending infection 2

• Anesthesia-related complications 2

Why Not Cerclage at 18 Weeks?

Waiting until 18 weeks for prophylactic cerclage is suboptimal because cervical changes may already be advanced by this gestational age, reducing cerclage effectiveness. 2

• If prophylactic cerclage is chosen (against current best evidence), it should be placed at 12-14 weeks, not 18 weeks 2

• By 18 weeks, patients with true cervical insufficiency may have already developed significant cervical shortening or funneling 2

Why Not Clinical Assessment of Cervical Dilation Alone?

Clinical digital cervical examination is insensitive for detecting early cervical changes and cannot visualize the internal os where pathologic changes first occur. 2

• Transvaginal ultrasound detects cervical shortening and funneling weeks before digital examination reveals dilation 2

• The internal os changes precede external os dilation, and only ultrasound can assess internal os funneling 2

• Clinical examination has poor reproducibility compared to ultrasound measurement 2

Critical Implementation Details

Ultrasound Technique

• Use transvaginal approach (not transabdominal) for cervical assessment 2

• Measure cervical length from internal to external os along the endocervical canal 2

• Document presence and extent of any cervical funneling 2

• Empty bladder before measurement to avoid false lengthening 2

Cerclage Placement When Indicated

• McDonald cerclage technique is standard for ultrasound-indicated cerclage 1

• Place cerclage as soon as threshold criteria are met (do not delay) 2

• Continue ultrasound surveillance after cerclage placement, though routine post-cerclage monitoring lacks strong evidence for benefit 2

Common Pitfalls to Avoid

• Do not wait for symptoms (bleeding, cramping, pressure) before initiating surveillance—cervical insufficiency is typically asymptomatic until advanced 2

• Do not rely on transabdominal ultrasound for cervical assessment—transvaginal approach is required for accurate measurement 2

• Do not delay cerclage placement once intervention thresholds are met—effectiveness decreases with advancing cervical changes 2

• Do not assume one prior loss mandates prophylactic cerclage—the evidence supports selective rather than universal cerclage 1

Additional Considerations

Progesterone Supplementation

• Consider vaginal progesterone supplementation if cervical shortening is detected, as this reduces preterm birth risk by 44% in patients with short cervix 2

• Progesterone can be used in conjunction with cerclage when indicated 2

Patient Counseling

• Explain that approximately 64% of patients with one prior second trimester loss will NOT require cerclage with ultrasound-guided management 1

• Discuss that outcomes are equivalent between prophylactic and ultrasound-indicated cerclage approaches 1

• Emphasize the importance of adherence to the surveillance schedule 2