The goal of this clinical trial is to determine whether cervical cerclage reduces the risk of preterm birth in patients with a short transvaginal ultrasound (TVU) cervical length (CL) ≤25mm between 24 0/7-26 6/7 weeks.

Singleton high-risk pregnancies < 24 weeks of gestation will be screened for enrollment and randomized, if a short TVU CL (≤25mm) is detected between 24 0/7 - 26 6/7 weeks, to either cervical cerclage or control (no cerclage). Aside from cerclage placement, management of included women will be the same including recommendation for continuing or initiating daily vaginal progesterone 200mg from randomization until 36 6/7 weeks. The primary outcome will be the incidence of preterm birth <37 weeks.

Inclusion Criteria:

• 18-50 years old, pregnant, assigned female at birth
• Singleton pregnancy
• TVU CL ≤25mm between 24 0/7 - 26 6/7 weeks of gestation

Exclusion Criteria:

• Initial multifetal gestation with subsequent multifetal pregnancy reduction, or selective fetal termination performed >14 weeks, or cotwin pregnancy loss diagnosed >14 weeks
• Cerclage in situ
• Preterm labor, defined as painful regular uterine contractions and change in cervical dilation
• PPROM
• Active vaginal bleeding
• Suspected intraamniotic infection
• Major fetal structural abnormality or chromosomal disorder
• Placenta previa or accreta
• Other contraindication to cerclage placement
• Participation in another clinical trial related to preterm birth prevention, cerclage, or progesterone