P03.14: Sonographic cervical length in prediction of preterm delivery: centiles versus single cut-offs measurements

to determine whether a single threshold of the sonographic cervical length or different cut-offs for each period of pregnancy are more sensitive in predicting preterm delivery. We observed 108 patients between the 10th and 34th week of gestational age admitted for threatened preterm labour. The cervical length was determined using ultrasound on admission. Exclusion criteria included multiple pregnancies, singleton pregnancies lacking sonographic determination of the gestational age prior to 22 weeks, ruptured membranes, cervical dilatation 33 cm at digital exploration, vaginal bleeding, placenta previa and prior cervical cerclage. Two cut-offs (15 and 25 mm) and two centiles (2.5° and 10°) of our reference curves were used for predicting delivery within 7 days and before 34 weeks. 76.8% of the patients delivered after 34 weeks, 23.1% before 34 weeks while in 17.5% of the cases delivery occurred within 7 days. The median cervical length at admission was 35 mm, 25 mm, and 21 mm respectively. Univariate analysis of the different cut-offs showed a higher odds ratio for 25 and 15 mm compared to the 2.5 and 10°P both in predicting delivery within 7 days and before 34 weeks. The diagnostic accuracy was statistically higher for the 15 and 25 mm thresholds both in predicting PTL within 7 days respectively 83 and 76% and before 34 weeks, 77 and 76% respectively. sonographic measurement of the cervical length proved to be a feasible and effective method in identifying the population with an increased risk for PTL both within 7 days and before 34 weeks following the exam. The negative predictive value resulted particularly high- 90% for the 25 mm cut-off and for the 2.5° and 10°P, giving a likelihood ratio of 93% and 91% respectively that delivery will probably not occur within 7 days. These elements obviously need to be integrated with clinical aspects of each case, for the optimal management of patients with suspected PTL.