What cervical length indicates high preterm risk?

CL <25 mm at 18-24 weeks in asymptomatic singletons has OR ~4-6 for spontaneous preterm birth <34 weeks. CL <15 mm is associated with PTB risk exceeding 50%. CL <20 mm in twins is high risk.

What treatment is indicated for short cervix?

Vaginal progesterone (200 mg nightly) reduces PTB risk by ~40-45% in singletons with CL <25 mm (Fonseca, Hassan trials). Cervical cerclage for CL <25 mm with prior PTB history. Arabin pessary has mixed evidence.

Is cervical length screening universal?

Universal CL screening at anatomy scan (18-24 weeks) is recommended by SMFM for singletons. Twins have different cutoffs. Asymptomatic universal screening identifies 40-60% of women who will benefit from prophylactic progesterone.

Cervical Length and Preterm Birth Risk Calculator

Calculate preterm birth risk from mid-trimester cervical length measurement. CL <25 mm at 18-24 weeks in singleton or CL <35 mm in twins increases preterm birth risk. Guides progesterone supplementation and cerclage decisions.

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