Recommended Management: Serial Ultrasound Assessment with Ultrasound-Indicated Cerclage
For a patient with one prior second-trimester loss due to cervical incompetence, begin serial transvaginal ultrasound assessment of cervical length starting at 14-16 weeks, and place ultrasound-indicated cerclage only if the cervix shortens to ≤25 mm before 24 weeks of gestation. 1
Why Not Prophylactic Cerclage at 13 or 18 Weeks?
History-indicated cerclage at a predetermined gestational age (12-14 weeks) should be reserved exclusively for patients with three or more second-trimester pregnancy losses or extreme premature deliveries without other identifiable causes. 2, 1 Your patient has only one prior loss, which does not meet this threshold for prophylactic intervention.
The critical pitfall to avoid is placing cerclage at arbitrary gestational ages without objective cervical assessment. 1 This approach leads to unnecessary interventions in the approximately 69% of high-risk women who maintain adequate cervical length throughout pregnancy and never require cerclage. 1
Why Serial Ultrasound is Superior to Clinical Assessment Alone
Transvaginal ultrasound is the reference standard for cervical assessment and is superior to clinical examination alone. 1 Clinical cervical dilation assessment (option C) is insufficient because it provides inadequate risk stratification and may miss early cervical shortening before dilation becomes clinically apparent. 1
The Evidence-Based Algorithm
Step 1: Initiate Monitoring
- Begin transvaginal ultrasound cervical length assessment at 14-16 weeks of gestation 1
- Continue monitoring every 2-3 weeks through 24 weeks of gestation 1
Step 2: Intervention Thresholds Based on Cervical Length
If cervical length ≤20 mm before 24 weeks:
- Prescribe vaginal progesterone 200 mg daily (GRADE 1A recommendation for patients with 1-2 prior second-trimester losses) 1
If cervical length 21-25 mm:
- Offer vaginal progesterone 200 mg daily through shared decision-making (GRADE 1B recommendation) 1
If cervical length ≤25 mm before 24 weeks in a patient with prior spontaneous preterm birth:
- Offer ultrasound-indicated cerclage placement 1
- This approach shows compelling benefit in patients with short cervix and previous preterm birth 2
If cervical length <10 mm:
- Cerclage shows particular benefit, with decreased preterm birth at <35 weeks (39.5% vs 58.0%) 1
- Consider ultrasound-indicated cerclage even if progesterone has already been initiated 1
Step 3: Post-Cerclage Management (If Cerclage Placed)
- Add vaginal progesterone 200 mg daily after cerclage placement, which reduces spontaneous preterm birth at <34 weeks (2.2% vs 18.4%) and <37 weeks (9.1% vs 29.7%) 1, 3
- Serial cervical length assessments after cerclage placement are not routinely recommended due to insufficient evidence supporting clinical benefit 2
What NOT to Do
Do not place cerclage routinely for cervical length 10-25 mm without cervical dilation (GRADE 1B recommendation against). 1 Meta-analysis shows no benefit in patients without prior preterm birth history who have cervical length in this range. 1
Do not use 17-alpha hydroxyprogesterone caproate (17-OHPC) for short cervix treatment (GRADE 1B recommendation against). 1
Do not place cervical pessary due to conflicting trial data and recent safety signals, including increased perinatal mortality (GRADE 1B recommendation against). 1
Special Consideration: When Physical Examination Matters
If ultrasound shows cervical length <11-15 mm, perform physical examination because 30-70% of these patients will have cervical dilation ≥1 cm, making them candidates for examination-indicated cerclage before 24 weeks. 1