Cervical cerclage for the prevention of preterm birth.

Contemporary evidence supports the concept that cervical insufficiency is anything but a well-defined and distinct clinical entity. Instead, it is only 1 component of the larger and more complex preterm birth syndrome. Premature cervical ripening, as evidenced by shortening and effacement beginning at the internal os, provides strong evidence that parturition has begun and is the result of multiple interrelated pathways and inciting factors. Ultrasonographic screening of the cervix and treatment with cerclage for cervical shortening in the mid-trimester is reserved for women with prior spontaneous preterm birth (Fig. 1). Although cerclage benefit increases as the cervix shortens to less than 25 mm, it is appropriate to offer cerclage to women with shortened cervical length of less than 25 mm, and particularly those with a coexistent U-shaped funnel.