Transvaginal sonography is yet another tool, and cervical length and the presence offunneling are sought. he latter is ballooning of the membranes into a dilated internal os, but with a closed external os. In women with these findings, early randomized trials were inconclusive in proving the clinical value of cerclage to prevent preterm birth (Rust, 2001; To, 2004). A multicenter randomized trial of 302 high-risk women with cervical length <25 mm reported that cerclage prevented birth before viability but not birth before 34 weeks (Owen, 2009). Subsequently, however, Berghella and coworkers (201i1) included ive trials in a metaanalysis and showed that cerclage for these high-risk women signiicantly reduced preterm birth before 24, 28, 32, 35, and 37 weeks.
Cervical length screening is now recommended by both the American College of Obstetricians and Gynecologists (2016b) and the Society for Maternal-Fetal Medicine (2015) for women with prior preterm birth. Between 16 and 24 weeks' gestation, sonographic cervical measurement is completed every 2 weeks. If an initial or subsequent cervical length is 25 to 29 mm, then a weekly interval is considered. If the cervical length measures <25 mm, cerclage is ofered to this group of women. Notably, for women without a history of preterm birth but with a short cervix incidentally identiied sonographically, progesterone therapy is ofered instead of cerclage.
With twin gestations, one retrospective analysis found no improved outcomes in women with a cervical length <25 mm (Stoval, 2013). he College (2016b) does not recommend the use of cerclage in twin pregnancies.
Contraindications to cerclage usually include bleeding, contractions, or ruptured membranes, which substantially raises the likelihood of failure. Thus, prophylactic cerclage before dilatation is preferable. Surgery between 12 and 14 weeks' gestation allows this early intervention yet avoids surgery in a woman with a irst-trimester pregnancy destined for spontaneous loss.
Preoperatively, screening for aneuploidy and obvious malformation is completed. Cervical secretions are tested for gonorrhea and chlamydial infection. hese and obvious cervical infections are treated.
At times, the cervix instead is found to be dilated, efaced, or both, and an emergent rescue cerclage is performed. However, there is debate as to how late this should be performed. The conundrum is that the more advanced the pregnancy, the greater the risk that surgical intervention will stimulate preterm labor or membrane rupture. At Parkland Hospital, cerclage procedures are generally not done once supposed fetal viability is reached after 23 to 24 weeks. Others, however, recommend placement later than this (Caruso, 2000; Terkildsen, 2003).