Management of Short Cervix in Twin Pregnancy
For twin pregnancies with a short cervix (≤25 mm) before 24 weeks, expectant management without progesterone, cerclage, or pessary is the only evidence-based approach. 1
Primary Recommendation
Do NOT use vaginal progesterone in twin pregnancies with short cervix—despite GRADE 1A evidence supporting its use in singletons with cervical length ≤20 mm, progesterone shows no benefit in reducing preterm birth rates in twins (SMFM 2024, GRADE 1B). 2, 1
Do NOT place cervical cerclage—randomized trials demonstrate no benefit and a trend toward harm in twin pregnancies with cervical shortening (SMFM 2024, GRADE 1B). 1, 3
Do NOT use cervical pessary—recent trials show no benefit in unselected twin populations or those with short cervix, with potential safety concerns including increased perinatal mortality (SMFM 2024, GRADE 1B). 2, 1, 4
Do NOT use 17-alpha-hydroxyprogesterone caproate (17-OHPC) or any other progestogen formulation for short cervix management in twins (SMFM 2024, GRADE 1B). 2, 1
Diagnostic Confirmation
Cervical length must be measured by transvaginal ultrasound using standardized technique (Perinatal Quality Foundation or Fetal Medicine Foundation protocols); transabdominal measurements are insufficient for clinical decision-making. 1
A cervical length <15 mm between 15-24 weeks represents a critical threshold that predicts preterm labor regardless of management strategy in twin pregnancies. 1
Chorionicity-Specific Considerations
Monochorionic twins have shorter mean cervical length (≈32.8 mm) compared to dichorionic twins (≈34.9 mm) and experience higher spontaneous preterm birth rates (53.1% vs 44.9%). 1
For any given cervical length measured between 18-23 weeks, monochorionic diamniotic pregnancies deliver approximately 2 weeks earlier than dichorionic pregnancies. 1
Surveillance Strategy
Do NOT perform routine transvaginal cervical-length screening after 25-26 weeks in multiple gestations—the predictive value declines substantially and no effective interventions exist at this stage (SMFM 2024, GRADE B). 1
Continue standard prenatal care protocols for twin gestations with routine monitoring. 1
Critical Pitfalls to Avoid
Never extrapolate singleton data to twins—interventions proven effective in singleton pregnancies (vaginal progesterone for CL ≤20 mm) have been specifically studied and shown ineffective in twin gestations. 1
Avoid the 20-mm threshold used in singletons—this cut-off is not validated for twins, and 85% of twins delivering <32 weeks have cervical length >20 mm at mid-gestation. 5
Recognize the poor predictive value—36% of twin pregnancies delivering <32 weeks have normal cervical length in mid-gestation, and cervical length shows only weak independent association with preterm birth in twins (AUC 0.65). 5
Do not offer cerclage based on cervical shortening alone—even in the high-risk setting of twin-twin transfusion syndrome requiring fetoscopic laser surgery, cerclage was associated with a 13-day reduction in pregnancy duration compared to expectant management. 3