In approximately 0.5-1% of pregnancies, pregnant women are diagnosed as having an incompetent cervix, usually based on a history of early pregnancy loss, often accompanied by painless dilatation. More recently, an incompetent cervix is diagnosed by cervical ultrasound - usually for being 'short'. A cerclage - a circumferential stitch placed in the cervix - has has been studied for a variety of obstetrical indications, including a history of three or more preterm births, second trimester loss, cervical shortening on ultrasound, preterm cervical dilation and being assessed as high risk for a preterm birth. The Royal College of Obstetricians and Gynaecologists conducted a randomized, controlled trial investigating 1292 women and demonstrated that cerclage reduced delivery prior to 37 weeks from 53 to 32% in women with either a prior second trimester loss or at least three previous preterm deliveries. The Cervical Incompetence Prevention Randomized Cerclage Trial (CIPRACT) published data supporting the screening of women with history of preterm delivery or second trimester losses via ultrasound to obtain transvaginal cervical length; these authors concluded that cerclage was indicated when cervical length was less than 2.5 cm. Berghella et al. performed a meta-analysis of ultrasound-indicated cerclage and reported that when cervical length was less than 2.5 cm between 14-23 6/7 weeks gestational age, a 40% reduction in preterm birth was observed in singletons receiving a cerclage. However, they found an increase in preterm birth when the same indication was used for cerclage placement in women with multiple pregnancies. Evidence of cervical inflammation as determined by a high IL-8 level may divide the population at risk into those that may benefit and those that may be harmed by cerclage placement. A large NIH-sponsored trial of cerclage in women with a prior preterm birth and a short cervix is currently underway, with the results expected soon.
Women's Health. 2008;4(6):625-638. © 2008 Future Medicine Ltd.
Cite this: Prevention of Preterm Birth - Medscape - Nov 01, 2008.