28th World Congress on Ultrasound in Obstetrics and Gynecology Poster discussion hub abstracts P17.03 Uterocervical angle measurement in the prediction of preterm birth in women presenting with threatened preterm labour J.M. Crane, K. Manning, D. O’Brien Obstetrics and Gynecology, Memorial University of New- foundland, Eastern Health, St John’s, NL, Canada Objectives: To determine if uterocervical angle (UCA), compared with cervical length (CL), is an independent predictor of spontaneous preterm birth (SPTB) in women with threatened preterm labour (TPTL). Methods: This retrospective cohort study included women with live singleton gestations and intact membranes who had an episode of TPTL, underwent transvaginal ultrasonographic CL (TVUSCL) assessment between 16 wk-29 6/7wk, and delivered Jul2007-Dec2016. UCA was measured retrospectively on ultrasound images. The primary outcome was SPTB<34wk, with secondary outcomes including SPTB<37wk and neonatal morbidity. Univariate analysis was used to compare demographic characteristics. ROC curve was generated to determine the best cut-off for UCA. Multiple logistic regression(MLR) was performed calculating ORs and 95%CIs, to identify independent predictors for the outcomes of interest. Results: 263 women underwent TVUSCL assessment, of whom 211(80.2%) had UCA measurement obtained. ROC curve found the best cut-off for UCA to be ≥125 o . Women who delivered <34wk were more likely to have a history of SPTB(43.8% versus 12.3%, p=0.003), CL<2.5cm(62.5% versus 15.9%, p<0.0001) and UCA≥125 o (62.5% versus 21.3%, p=0.002). MLR found the independent predictors of SPTB<34wk to be CL<2.5cm(OR 7.37,95%CI2.42-22.43, p<0.0001) and history of SPTB(OR 4.12,95%CI1.39-13.06, p=0.016). Independent predictors of SPTB<37wk included CL<2.5cm(OR 11.43,95%CI4.80-27.23, p<0.0001), history of SPTB(OR 3.07 95%CI1.07-8.84, p=0.038) and history of LEEP(OR 2.97,95%CI1.02-8.69, p=0.047). Inde- pendent predictors of neonatal morbidity were CL<2.5cm(OR 5.33,95%CI2.22-12.79, p<0.0001) and history of SPTB(OR 3.75,95%CI1.43-9.81, p=0.009). UCA was not an independent predictor in any of the models. Conclusions: Although a wide UCA≥125 o in women with singleton gestations presenting with TPTL is associated with SPTB<34wk, it is not as good as CL in predicting SPTB<34k, <37wk or neonatal morbidity. Further research is needed to determine if this measurement is useful in other populations. P17.04 Factors for prevention of previable delivery following rescue cerclage S. Jung, S. Kim, Y. Cho, E. Seo, S. Kong, R. Lee Obstetrics and Gynecology, Gachon University Gil Medical Centre, Incheon, Republic of Korea Objectives: To evaluate factors associated with previable delivery after cerclage in women protruding amniotic membrane. Methods: The retrospective cohort study was conducted in 55 women with protruding amniotic membrane whom underwent McDonald cerclage and were delivered by a single surgeon between January 2006 and June 2017. They were grouped based on 24+0 weeks gestation at delivery. We compared clinical characteristics and association factors affected previable delivery after recue cerclage. Results: Twenty women delivered before 24+0 weeks gestation and 35 women delivered at or after 24weeks gestation. Gestational age at cerclage was earlier (20.4 versus 22.7 weeks, p=0.003) and latency period after cerclage (0.9 versus 10.2 weeks, p<0.001) was shorter in delivered before 24 weeks. Postoperative white blood cell (12755 versus 10230, p=0.006) and C-reactive protein (1.8 vs. 1.4, p=0.049) were elevated and cerclage height, length from cerclage stitch to internal os, was shorter (0.7 versus 1.3cm, p=0.005) while cervical length after cerclage was not differ significantly in delivered before 24 weeks. (1.4 versus 2.2cm, p=0.058). After adjusting for confounding factors, cerclage height (OR 4.116; 95% CI: 1.078-15.711) and gestational age at cerclage (OR 1.545; 95% CI: 1.120-2.131) were associated with a higher likelihood whereas postoperative C-reactive protein level was reduced likelihood (OR 0.620; 95% CI: 0.391-0.982) of reaching at least 24 weeks gestation. Conclusions: Longer cervical height increases prolongation of preg- nancy at least until 24 weeks significantly. Elevated postoperative C-reactive protein and earlier diagnosed bulging amniotic membrane are associated with previable birth. P17.05 Does a LLETZ procedure have a significant effect on ultrasonographic length/consistency in the second trimester of pregnancy? J.S. Woo, R. Mogra, J. Hyett RPA Women and Babies, Royal Prince Alfred Hospital, Camperdown, NSW, Australia Objectives: Ultrasound is commonly used to assess risk for preterm birth (PTB) at 16-22 weeks’ gestation. One cohort considered to be high risk – who may therefore be screened – are women who have had a large loop excision of the transformation zone (LLETZ) procedure. This procedure may in itself impact on cervical length and tissue consistency, two features that are typically used to assess the risk of PTB. These tools may therefore not be appropriate in a population of women that had a LLETZ. We assessed cervical length and consistency in women who had a LLETZ and a series of normal controls. Methods: We prospectively recruited cohorts of women who had a LLETZ (n=20) or who had not had this procedure (n=50) (or any other risk factors for PTB). The cervix was assessed by transvaginal ultrasound and measures of cervical length and elastography were recorded (Toshiba Aplio 500; 3–11 mHz TV transducer). Baseline characteristics and measures of elastography were assessed using Mann Whitney U tests and logistic regression. Results: The controls were assessed at 19.3 (IQR 18.9-19.6) weeks’ gestation and the LLETZ cases at 18.4 (IQR 15.9-21.4) weeks (n/s difference). Cervical length was significantly shorter in the LLETZ cohort (32.7; IQR 29.5-35.0) vs. (35.2: IQR 33.0-37.0) p<0.01. In the normal cohort, there was a small reduction in P17.04: Table 1. Influencing factors to delivery at or after 24 weeks of gestation following rescue cerclage < 24 weeks ≥24 weeks OR (95% CI) P-value Gestational age at cerclage 20.4(18.3-21.5) 22.7(20.5-24.1) 1.545(1.120-2.131) 0.008 Cervical length 1.4(0-2.4) 2.2(1.8-2.7) 0.61(1.186-2.069) 0.439 Cerclage height 0.7(0-1.4) 1.3(1.1-1.5) 4.116(1.078-15.711) 0.038 Postoperative WBC 12755(10330-14927) 10230(9010-12360) 1.0(1.0-1.0) 0.207 Postoperative CRP 1.8(1.2-5.1) 1.4(0.5-2.2) 0.620(0.391-0.982) 0.042  The Authors 2018 182  Ultrasound in Obstetrics & Gynecology 2018; 52 (Suppl. 1): 138–193.