Is an ultrasound for cervical length appropriate for a patient with a cerclage (cervical cerclage) in place who is contracting at 34 weeks gestation?

Ultrasound for Cervical Length in Cerclage Patients at 34 Weeks with Contractions

At 34 weeks gestation with contractions, ultrasound cervical length assessment is not appropriate for a patient with cerclage in place, as routine surveillance beyond 28 weeks lacks evidence of clinical benefit and would not change management at this gestational age. 1, 2

Why Cervical Length Ultrasound is Not Indicated

Insufficient Evidence for Routine Surveillance After Cerclage

• The Society for Maternal-Fetal Medicine explicitly does not recommend routine cervical length surveillance in patients with cerclage because there are insufficient data supporting clinical benefit to screening. 1
• Serial cervical length assessments after cerclage placement are not routinely recommended due to lack of evidence that screening improves outcomes. 3
• Routine surveillance should be discontinued after 28 weeks, as there is insufficient evidence of clinical benefit beyond this gestational age. 2

Gestational Age Considerations at 34 Weeks

• At 34 weeks, the patient is beyond the window where cervical length findings would alter management—interventions like progesterone or cerclage adjustment are not indicated at this late gestational age. 1
• The primary concern at 34 weeks with contractions is whether the patient is in active preterm labor, which requires clinical assessment (cervical examination, contraction monitoring, fetal assessment) rather than ultrasound cervical length measurement. 4

What Should Be Done Instead

Focus on Clinical Assessment of Preterm Labor

• Evaluate for active preterm labor through sterile speculum examination to assess cervical dilation, effacement, and membrane status. 4
• Monitor contraction pattern and fetal well-being with continuous fetal monitoring.
• Consider fetal fibronectin testing if clinical examination is equivocal and the patient has not had recent cervical examination or intercourse.

Management at 34 Weeks Gestation

• If true preterm labor is confirmed at 34 weeks, the focus shifts to delivery preparation rather than prolonging pregnancy, as neonatal outcomes at 34 weeks are generally favorable.
• Corticosteroids for fetal lung maturity are typically not indicated at 34 weeks unless there are specific institutional protocols for late preterm births.
• Group B streptococcus prophylaxis should be administered if indicated.

Common Pitfalls to Avoid

• Do not order cervical length ultrasound reflexively in cerclage patients presenting with contractions after 28 weeks—it will not change management and lacks evidence of benefit. 1, 2
• Do not confuse surveillance protocols for high-risk patients without cerclage with post-cerclage management—the evidence base differs significantly between these populations. 1
• Avoid using transabdominal ultrasound if cervical assessment is deemed necessary—transvaginal or transperineal approaches are required for accurate cervical evaluation. 2