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Cerclage for short cervix on ultrasonography: meta-analysis of trials using individual patient-level data.

Objective: Preterm birth is the main cause of perinatal morbidity and mortality. A short cervical length on transvaginal ultrasonography predicts preterm birth. Our aim was to estimate by meta-analysis of randomized trials whether cerclage prevents preterm birth in women with a short cervical length. Data Sources: MEDLINE, PubMed, EMBASE, and the Cochrane Library were searched with the terms “cerclage,” “cervical cerclage,” “short cervix,” “ultrasound,” and “randomized trial.” We included randomized trials involving the use of cerclage in women with short cervical length on transvaginal ultrasonography using patient-level data. Tabulation, Integration, and Results: Four properly conducted trials were identified. In the total population, preterm birth at less than 35 weeks of gestation occurred in 29.2% (89/305) of the cerclage group, compared with 34.8% (105/302) of the no-cerclage groups (relative risk [RR] 0.84, 95% confidence interval [CI] 0.67–1.06). There was no significant heterogeneity in the overall analysis (P = .29). There was a significant reduction in preterm birth at less than 35 weeks in the cerclage group compared with the no-cerclage groups in singleton gestations (RR 0.74, 95% CI 0.57–0.96), singleton gestations with prior preterm birth (RR 0.61, 95% CI 0.40–0.92), and singleton gestations with prior second-trimester loss (RR 0.57, 95% CI 0.33–0.99). There was a significant increase in preterm birth at less than 35 weeks in twin gestations (RR 2.15, 95% CI 1.15–4.01). Conclusion: Cerclage does not prevent preterm birth in all women with short cervical length on transvaginal ultrasonography. In the subgroup analysis of singleton gestations with short cervical length, especially those with a prior preterm birth, cerclage may reduce preterm birth, and a well-powered trial should be carried out in this group of patients. In contrast, in twins, cerclage was associated with a significantly higher incidence of preterm birth.

Prediction of patient-specific risk of early preterm delivery using maternal history and sonographic measurement of cervical length: a population-based prospective study.

To develop a model for calculating the patient‐specific risk of spontaneous early preterm delivery by combining maternal factors and the transvaginal sonographic measurement of cervical length at 22 + 0 to 24 + 6 weeks, and to compare the detection rate of this method to that achieved from screening by cervical length or maternal characteristics alone.

Cervical length and obstetric history predict spontaneous preterm birth: development and validation of a model to provide individualized risk assessment.

To evaluate the ability of combinations of cervical length and maternal history to assess the risk of spontaneous preterm birth, and to provide a simple procedure for the optimal estimation of risk.

OC140: Assessing the risk of spontaneous preterm birth using ultrasonic cervical length measurement and maternal characteristics

measurement of the cervix better reflects the engineering principle that greater tissue volume equals greater resistance to dilatation than cervical length. The aim of the study was to determine if cervical volume is a more reliable predictor of preterm delivery than cervical length. Methods: Patients were recruited between 19 and 34 weeks’ gestation if they were shown to have uterine contractions and/or cervical change as determined by pelvic examination or abnormally short (< 28 mm) cervical length. The cervical length and cervical volume were obtained using standard transvaginal 2D and 3D study. Delivery information was subsequently obtained. Data pertaining to cervical length and cervical volume were analyzed postpartum. Results: To date, cervical length, cervical volume and outcome parameters are available for 37 patients. Twenty-two of these patients delivered preterm (< 37 weeks GA). The mean gestational age at delivery (preterm) was 31.4 + 4.1 weeks. Mean maternal age was 22.28 + 6.67 years. Cervical volume was more predictive of risk for preterm delivery than cervical length (sensitivity 95.5%, specificity 73.4%, positive predictive value 84%, negative predictive value 91.7%). Based on the limited data available to date, ROC analysis demonstrated that cervical volume is a better predictor of preterm delivery risk. The area under the curve was 854 for cervical volume vs. 721 for cervical length. Conclusions: Our data strongly suggest that cervical volume is a better predictor of preterm delivery than cervical length. We continue to actively recruit patients to reach the number of patients needed statistically to conclude the study.

OC186: Cervical length at mid-gestation and the risk of primary Cesarean section at term

aim of this study was to explore the value of 3DXI in the evaluation of these structures in the mid-trimester. Methods: Twenty women who presented for a detailed secondtrimester scan agreed to participate in this study, all of whom had normal infants at birth. Ultrasonographic examination was performed with a high-resolution 3D ultrasound machine (Accuvix XQ, Medison). A mechanical broadband transabdominal transducer was used to obtain volumes from the fetal brain (n = 20) and the fetal heart (n = 20) using a 65◦ sweep. Volumes were analyzed offline using 3DXI PC Viewer software and the following brain structures were assessed: both lateral ventricles, third ventricle, cavum septum pellucidum, cerebellum and cisterna magna. Similarly, the following cardiac structures were also evaluated: four-chamber view, outflow tracts (aorta and pulmonary artery), and the three vessels in the upper mediastinum. Results: Regarding the brain structures, one atrium was identified in 20 of the cases (100%), two atria in 18 (90%), the third ventricle in 14 (70%), the cerebellum in 18 (90%), the cisterna magna in 18 (90%) and the corpus callosum in seven (35%). Regarding the cardiac structures, the four-chamber view was visualized in all 20 (100%), the aortic outflow tract in 19 (95%), the pulmonary artery outflow tract in 19 (95%) and the three-vessel view in 18 (90%). Conclusions: 3DXI technology allows interrogation of a single volume of information in multiple planes so that sequential planes of the fetal anatomy can be evaluated at a glance. As the quality of 3D images is highly dependent on the quality of the conventional two-dimensional image, reconstruction of structures in the cerebral midline in the third plane, such as the corpus callosum, may be unreliable.

OC87: Uterine artery Doppler and cervical assessment in the prediction of early preterm delivery

Objective: To examine the value of combining maternal history with cervical length and uterine artery Doppler at 22–24 weeks in the prediction of early preterm delivery. Methods: This was a prospective multicentre observational study in seven hospitals in London, UK. We used transvaginal sonography to measure cervical length and uterine artery pulsatility index (PI) at 22–24 weeks in singleton pregnancies. Logistic regression was used to determine the contribution of maternal characteristics, previous obstetric history, cervical length and uterine artery PI in the prediction of delivery before 33 weeks. Results: 32,150 women were recruited and 1,373 women (4.3%) were lost to follow-up. Delivery before 33 weeks occurred in 439 (1.4%) women, including spontaneous or iatrogenic delivery of stillbirths in 52 (0.2%) cases, spontaneous delivery of live births in 238 (0.8%) and iatrogenic delivery of live births in 149 (0.5%). For a 5% false positive rate, the detection rate of spontaneous early delivery was 30% for maternal factors and this was improved to 50% by combining maternal factors with cervical length. Similarly, for iatrogenic delivery and fetal death, the detection rate was improved from 44% and 33% respectively from maternal history alone to 81% and 67% respectively with the addition of uterine artery PI. Conclusion: The combination of maternal history, cervical length and uterine artery PI at 22–24 weeks can identify a high proportion of women that subsequently deliver before 33 weeks.