OP34.07: Is a short cervix initially diagnosed in the early third trimester a risk factor for subsequent histologic chorioamnionitis and preterm delivery in twin gestations?

To determine whether a short cervix (defined as a cervical length ⩽ 25mm) initially diagnosed in the early third trimester is associated with increased risk of subsequent histologic chorioamnionitis and spontaneous preterm delivery ( < 35 weeks) in twin gestations. This was a prospective study involving 145 consecutive women with twin gestations attending for routine antenatal care who underwent transvaginal ultrasound at 20–25 weeks and 28–30 weeks for evaluation of cervical length. Inclusion criteria were 1) cervical length more than 25 mm at 20–25 weeks; 2) placental histologic examination after delivery; 3) no history of prior or subsequent cervical cerclage. The primary outcomes were subsequent histologic chorioamnionitis and preterm delivery. The cervical length of ⩽ 25mm at 28–30 weeks was present in 20% (29/145) of women without a short cervix at 20–25 weeks. The prevalence of subsequent acute histologic chorioamnionitis was in 8% (11/145) and that of spontaneous preterm delivery was 5% (7/138). Women who were initially diagnosed a short cervix at 28–30 weeks were significantly more likely to have subsequent histologic chorioamnionitis and spontaneous preterm delivery than those who were not. The mean cervical lengths at 20–25 weeks and 28–30 weeks were significantly shorter in women who delivered preterm than in those who delivered at term. In twin gestations, a short cervix initially detected by transvaginal ultrasound at 28–30 weeks is associated with an increased risk of the subsequent histologic chorioamnionitis and the occurrence of spontaneous preterm delivery. Our findings support the hypothesis that a short cervix in asymptomatic pregnant women predisposes to ascending intrauterine infection.