Initial Cervical Length Research Articles

Serial Cervical Length Measurement for Determining the Risk of Preterm Labor: A Prospective Study

Objective: This study aimed to evaluate whether serial evaluations of cervical length (CL) have the potential to determine preterm labor in women with threatening preterm labor (TPL). Materials and Methods: This prospective study included pregnant women at 24 to 37 weeks of gestation referred to our institute because of TPL. Cervical length was measured at three successive time points using transvaginal sonography (upon admission, one-, and two-weeks post-admission). Data were analyzed using both parametric and non-parametric statistics. Results: The mean age of the 126 patients included was 25.60 ± 6.48 years, with age ranging from 14 to 42 years. The mean pregnancy age, at the time of the sonogram, was 33.54 ± 2.78 weeks. The initial CL had an area under the receiver operating characteristic curve (AUROC) of 0.854. The CLs measured one and two weeks later had AUROCs of 0.868 and 0.870, respectively. Based on these data, the cut-off points of 28.5 and 27.5 mm were identified for the initial and subsequent two-week CL measurements, respectively, capable of predicting preterm delivery. If the CL measured at initial admission was >28.5 mm, the likelihood of timely delivery was 92.22%. However, if the CL measured at initial admission was <28.5 mm, the chance of premature preterm delivery increased by 2.3 times. Patients with a CL <27.5 mm in the second week were 18.75% more likely to have a preterm delivery. If the CL was >27.5 mm, the probability of timely delivery was 89.7%. Conclusion: In this cohort of women, serially measured CLs taken during transvaginal sonography demonstrated promise as a method for indicating the possible risk of preterm delivery. Thus, measured CL may be a useful diagnostic component for prenatal care, as well as for classifying the risk of preterm delivery. Nevertheless, further studies are required to confirm the effectiveness and safety of these sonographic measures in larger and more diverse patient cohorts.

The effectiveness of cervical cerclage in twin pregnancies with a mid-trimester short cervix: A retrospective cohort study

ObjectiveTo analyze the effectiveness of cerclage in twin pregnancies with a short cervix. Study designRetrospective cohort study performed in two University Institutions in Valencia (Spain) with two different protocols for the management of asymptomatic dichorionic diamniotic twin pregnancies with mid-trimester cervical length ≤ 25 mm: treatment with indomethacin, antibiotics and cerclage (cerclage group) (N = 43) versus expectant management (control group) (N = 37). ResultsThe initial cervical length was similar in both groups but detection of a short cervix was performed earlier in the cerclage group (21.6 vs 24.1 weeks, p < 0.001). Women with cerclage had a greater pregnancy latency (12.5 vs. 7.7 weeks, p < 0.001); higher gestational age at delivery (34.1 vs. 31.8 weeks, p < 0.04); less spontaneous preterm birth (SPB) < 28 weeks (11.6 % vs 37.8 %, p < 0.009); higher birthweight (2145 vs 1733 g, p < 0.001); lower birthweight < 1500 g (12.5 % vs 40.0 %, p < 0.001); less admissions to the neonatal intensive care unit (NICU) (24.1 % vs 43.3 %, p < 0.03); shorter stay at NICU (25.6 vs 49.4 days, p < 0.02); lower respiratory distress requiring mechanical ventilation (14.9 % vs 36.5 %, p < 0.02); fewer patent ductus arteriosus (8.9 % vs 26.9 %, p < 0.008); and lower composite adverse neonatal outcome (26.6 % vs. 44.8 %, p < 0.03). Cerclage and gestational age at diagnosis were the only independent predictors of SPB < 32 and < 28 weeks by multivariate analysis. The cumulative data in the literature show promising beneficial effects of cerclage. ConclusionOur data suggest that cerclage in asymptomatic twin pregnancies with a short cervix may reduce the earliest SPB and may improve neonatal outcome.

Relationship between plasma concentration of 17-hydroxyprogesterone caproate and gestational age at preterm delivery

The effectiveness of 17-hydroxyprogesterone caproate is unclear as trials have provided conflicting results. With the absence of fundamental pharmacologic studies addressing dosing or the relationship between drug concentration and gestational age at delivery, the effectiveness of the medication cannot be evaluated. This study aimed to evaluate the relationship between plasma concentrations of 17-hydroxyprogesterone caproate and preterm birth rates and gestational age at preterm delivery and to assess the safety of the 500-mg dose. This study recruited 2 cohorts with previous spontaneous preterm birth; 1 cohort (n=143) was randomly assigned to either 250-mg or 500-mg 17-hydroxyprogesterone caproate, and the other cohort (n=16) was receiving the 250-mg dose for routine care. Steady-state trough plasma concentrations of 17-hydroxyprogesterone caproate obtained at 26 to 30 weeks of gestation were correlated to dose, spontaneous preterm birth rates, and measures of gestational length. Furthermore, maternal and neonatal safety outcomes were evaluated according to dose. There was a dose proportional increase in trough plasma concentrations with the 250-mg (median, 8.6 ng/m; n=66) and 500-mg (median, 16.2 ng/mL; n=55) doses. In 116 compliant participants with blood samples, drug concentration was not related to the spontaneous preterm birth rate (odds ratio, 1.00; 95% confidence interval, 0.93-1.08). However, there was a significant relationship between drug concentration and both the interval from the first administration to delivery (interval A: coefficient, 1.11; 95% confidence interval, 0.00-2.23; P=.05) and the interval from the 26- to 30-week blood draw to delivery (interval B: coefficient, 1.56; 95% confidence interval, 0.25-2.87; P=.02). The spontaneous preterm birth rate or measures of gestational length were not related to dose. Postenrollment cerclage adversely affected all pharmacodynamic assessments because it was a powerful predictor of spontaneous preterm birth (odds ratio, 4.03; 95% confidence interval, 1.24-13.19; P=.021) and both measures of gestational length (interval A [coefficient, -14.9; 95% confidence interval, -26.3 to -3.4; P=.011] and interval B [coefficient, -15.9; 95% confidence interval, -25.8 to -5.9; P=.002]). Initial cervical length was significantly related to the risk of postenrollment cerclage (odds ratio, 0.80; 95% confidence interval, 0.70-0.92; P=.001). Maternal and neonatal safety outcomes were similar in both dosing groups. In this pharmacodynamic study, trough plasma 17-hydroxyprogesterone caproate concentrations were significantly associated with gestational age at preterm birth but not with the preterm birth rate. Postenrollment cerclage was a powerful predictor of spontaneous preterm birth rate and gestational length. Initial cervical length predicted the risk of postenrollment cerclage. Adverse events were similar with the 500-mg and 250-mg doses of 17-hydroxyprogesterone caproate.

Cerclage versus vaginal progesterone in low-risk pregnant women with a short cervix

Objective To compare vaginal progesterone to cerclage in preventing preterm birth and adverse perinatal outcomes in women with a singleton gestation, incidentally found sonographic cervical length of <15 mm, and no history of preterm birth. Study design A retrospective cohort study was conducted on 68 women who delivered at the University of Kansas Health System with a singleton gestation found to have a cervical length <15 mm on transvaginal ultrasound and no history of preterm birth. Women treated with vaginal progesterone (n = 29) were compared to women who underwent cerclage placement (n = 39). The primary outcome was preterm birth at <34 weeks of gestation. Secondary outcomes include preterm birth at <37 and <28 weeks of gestation and neonatal morbidities. Results Of the 268 patients who had a cervical length of <15 mm on transvaginal ultrasound, 68 participants met inclusion criteria and were included in the final analysis. Twenty-nine participants received vaginal progesterone and 39 participants received cervical cerclage. The average cervical length at initiation of therapy was greater in the progesterone cohort versus cerclage cohort, respectively (10.5 vs. 8.0 mm, p < .01). All other baseline characteristics were similar between groups, including no difference in average gestational age at initiation of therapy (21.6 vs. 21.5 weeks, p = .87). Average latency after therapy did not differ between groups (100 vs. 92.7 days p = .43). The incidence of preterm birth at <37 weeks (OR = 1.49, 95% CI = 0.57–3.93), <34 weeks (OR = 1.47, 95% CI = 0.52–4.18), and <28 weeks (OR = 1.90, 95% CI = 0.45–8.07), did not differ significantly between groups. Additionally, no difference in neonatal morbidity was detected. Conclusion At our institution, we found no difference between vaginal progesterone and cerclage in the average latency period or risk of preterm birth among women with an incidental short cervix of <15 mm and no history of preterm birth, despite the significantly shorter initial cervical length in the cerclage group. These findings suggest either vaginal progesterone or cerclage could be used to reduce the risk of preterm birth among this high-risk population.

Performance of the cervical shortening for prediction of spontaneous preterm birth in uncomplicated twins

Objective There is a lack of consensus about the management of twins with significant cervical length (CL) shortening, especially if CL is above 25 mm. Therefore, it is important to define “abnormal” CL change over time, and to compare the performance of different strategies. The aim of this study was twofold, to describe the performance of the cervical shortening and that of an integrated strategy that includes both the cervical shortening and a fixed CL cutoff <25 mm in any measurement as predictor of spontaneous PTB (sPTB) < 34 weeks in uncomplicated twin pregnancies. Material and methods Retrospective cohort study of twins followed in our Twins Clinic at Hospital Italiano de Buenos Aires from 2013 to 2017. Inclusion criteria were dichorionic or monochorionic diamniotic twins with CL measurement between 18 and 33 + 6 weeks with available data of the delivery. Exclusion criteria included any of the following complications: iatrogenic preterm delivery <34 weeks, cerclage, fetal growth restriction, fetal death, structural anomalies, polyhydramnios, twin–twin transfusion syndrome, selective fetal growth restriction, twin anemia–polycythemia sequence, and twin reversed arterial perfusion sequence. Spontaneous preterm birth was defined as spontaneous delivery <34 weeks. Cervical shortening was analyzed in the following periods: 20–24 weeks, 20–28 weeks, 24–28 weeks, 24–32 weeks and 28–32 weeks. Cervical changes were analyzed as velocity of shortening over time (mm/week) and as the ratio of shortening over time (%/week). ROC curves for each period were constructed and two different cutoffs were used to classify changes of the CL as positive or negative screening: a) the shortening of CL associated to the highest value of the Youden Index and b) fixing a 10% false positive rate (FPR). For the second objective, we analyzed an integrated strategy considering a fixed cutoff of 25 mm at any GA and/or a significant shortening. The screening was considered positive if any CL measurement was <25 mm at any GA or there was a shortening of the CL ≥ the cutoff obtained for each period. We report sensitivity, specificity, positive and negative predictive value, positive and negative likelihood ratio and area under the ROC curve. Results We included 378 patients and 1417 measurements, 284 (75%) dichorionic and 94 (25%) monochorionic. Between 20 and 28 weeks, with a change in CL cutoff = 1.6 mm/week or 4.1%/week the detection rate was 54.2% (32.8–74.4%) and the specificity 80.5% (75.1–85.1%) and 83.5% (78.5–87.8%) respectively. In the integrated strategy, the detection rate was 65.7% (47.8–80.9%) and the specificity 69 (63.7–74). All the ROC curves of the periods studied showed an AUC < 0.7. In the group of patients that delivered preterm the initial mean CL was shorter than in the term group, 39 (±12) mm vs. 43 (± 7.7) mm (p = .02) and the most important change in CL was at 20–24 weeks both in the velocity and in the ratio of shortening over time. Conversely, patients that delivered at term showed a higher change in CL in the third trimester. Conclusion The performance of all the strategies analyzed as a predictor of sPTB <34 weeks was moderate. The period 20–28 weeks detected half of the patients at risk with a FPR around 10–20% and the integrated strategy increased the sensitivity up to a detection of two thirds of the patients at risk but with a FPR of ∼30%. Future analyses need to explore other strategies to improve the performance and to really identify the patients at higher risk.

Utility of follow-up cervical length screening in low-risk women with a cervical length of 26 to 29 mm

In women with a previous preterm birth, a protocol for serial cervical length screening has been studied and recommended for the identification and treatment of a short cervix. Cervical length screening along with vaginal progesterone has been suggested for low-risk women with singleton pregnancies to treat a short cervix and reduce preterm birth. However, specific protocols for single vs serial ultrasound measuring cervical length in this population are not established. Cost-effectiveness of universal cervical length screening depends on the cost of screening; follow-up of borderline measurements can contribute to increased costs with uncertain benefit. This study aimed to determine the utility of follow-up cervical length screening in otherwise low-risk women with singleton pregnancies with a midtrimester cervical length measurement of 26 to 29 mm through the assessment of the rate of short cervix (≤25 mm) on follow-up ultrasound and subsequent delivery outcomes. This was a 2-year retrospective cohort study at a single urban institution of women with singleton pregnancies with no previous spontaneous preterm birth and an initial transvaginal ultrasound cervical length measurement of 26 to 29 mm identified during universal cervical length screening at time of anatomy ultrasound (18 0/7 to 22 6/7 weeks' gestation). The primary outcome was the rate of short cervix (defined as ≤25 mm on transvaginal ultrasound) on follow-up ultrasound at <24 weeks' gestation. Secondary outcomes included the rate of spontaneous preterm birth (<37 and <34 weeks' gestation). During the study period, there were 2801 women with singleton pregnancies at 18 0/7 to 22 6/7 weeks' gestation with transvaginal ultrasound cervical length screening at time of anatomy scan. Among those women, 201 had a cervical length of 26 of 29 mm, and 184 (7%) had no previous spontaneous preterm birth and were included in the study. Furthermore, 144 women (78%) had a follow-up cervical length completed before 24 weeks' gestation. The mean follow-up interval was 1.5±0.6 weeks. Overall, the percentage of short cervix (≤25 mm) on follow-up was 15% (n=21). Baseline characteristics were similar, but the initial cervical length measurement was shorter in women who subsequently developed a short cervix (26.7±0.8 vs 27.8±1.0; P<.01). Delivery outcomes were available for 126 patients. The rate of spontaneous preterm birth at <37 weeks' gestation in women with an initial cervical length 26 to 29 mm and subsequent short cervix was significantly higher than the rate of spontaneous preterm birth in a historical cohort of low risk women with an initial cervical length >25 mm (16% vs 3%; P=.03). The rate of spontaneous preterm birth at <34 weeks' gestation in women with a subsequent short cervix was 11% (2 of 19). Here, approximately 15% of low-risk women with singleton pregnancies with a midtrimester cervical length measurement of 26 to 29 mm will experience cervical shortening of ≤25 mm before 24 weeks' gestation. Compared to women with singleton pregnancies without a history of preterm birth, the rate of spontaneous preterm birth (16%) in women with an initial cervical length of 26 to 29 mm and a subsequent cervical shortening of ≤25 mm is significantly higher. A total of 111 follow-up ultrasounds measuring cervical length would be required to prevent 1 early preterm birth at <34 weeks' gestation.

978 Cerclage versus vaginal progesterone in low risk pregnant women with a short cervix

To compare vaginal progesterone to cerclage in preventing preterm birth and adverse perinatal outcomes in women with a singleton gestation, incidentally found sonographic cervical length of <15 mm, and no history of preterm birth. A retrospective cohort study was conducted on 68 women who delivered at the University of Kansas Health System with a singleton gestation found to have a cervical length <15 mm on transvaginal ultrasound and no history of preterm birth. Women treated with vaginal progesterone (n=29) were compared to women who underwent cerclage placement (n=39). The primary outcome was the difference in average latency period. Secondary outcomes include preterm birth < 37, <34, and <28 weeks, and neonatal morbidities. Of the 268 patients who had a cervical length of <15 mm on transvaginal ultrasound, 68 participants met inclusion criteria and were included in the final analysis. Twenty-nine participants received vaginal progesterone and 39 participants received cervical cerclage. The average cervical length at initiation of therapy was greater in the progesterone cohort (10.5 mm vs 8.0 mm, p<0.01). All other baseline characteristics were similar between groups, including no difference in average gestational age at initiation of therapy (21.6 weeks vs. 21.5 weeks, p=0.87). Average latency after therapy did not differ between groups (100 days vs. 92.7 days p=0.43). The incidence of preterm birth at <37 weeks (41.4% vs. 51.3%), <34 weeks (27.6% vs. 35.9%), and <28 weeks (10.3% vs. 18%), did not differ significantly between groups. Additionally, no difference in neonatal morbidity was detected. At our institution we found no difference between vaginal progesterone and cerclage in the average latency period or risk of preterm birth among women with an incidental short cervix of < 15 mm and no history of preterm birth, despite the significantly shorter initial cervical length in the cerclage group. These findings suggest either vaginal progesterone or cerclage could be used to reduce the risk of preterm birth among this high risk population.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

17-P for Women With Congenital Uterine Anomalies: Does it Impact Preterm Birth Risk? [01K

INTRODUCTION: The effectiveness of 17P in the prevention recurrent of preterm birth (PTB) among women with congenital uterine anomalies (CUA) is unknown. This study evaluate association between 17P and delivery gestational age among women with CUA and a previous spontaneous PTB. METHODS: This study is a retrospective cohort of women with CUA who delivered at 2 health systems from 2013-2019. Women with ≥1 prior spontaneous PTB carrying non-anomalous, singleton gestations were included. The primary outcome was delivery gestational age. Secondary outcomes included delivery &lt;37 and &lt;34 weeks. Women receiving 17P were compared to those who did not receive 17P using Wilcoxon rank sum, Fisher’s exact, and chi-square. RESULTS: Of the 48 women with prior PTB, 11 (22.9%) received 17P. Demographic, medical, and obstetric characteristics were similar between women who did and did not get 17P. The subtype of CUA was also similar by 17P status. The initial cervical length was more than 35mm in both groups and did not differ, nor did rates of PPROM (25% vs 12.5%, 0.63). The median delivery gestational age was similar between groups [37.7 (IQR 30.7-38.3) vs. 37.1 (IQR 31-38.4) weeks] for those who did and did not receive 17P, respectively. Rates of recurrent PTB 0.99) and 0.99) were also similar in those who did and did not receive 17P. CONCLUSION: In this cohort of women with prior PTB and CUA, recurrent PTB was common, and though 17P was used in fewer than 1 in 4 women, use of 17P did not appear to impact this risk.

398: Is real-time dynamic cervical shortening predictive of preterm birth?

We aimed to assess the risk of preterm birth in those with dynamic cervical change. A retrospective matched case-control study. The study group comprised all women with dynamic cervical shortening (≥4 mm) noted from 24 to 34 weeks of gestation during 2010-2017 at a university hospital. Two control groups of women were established by matching the minimal and maximal cervical length measured, as well as age, parity, gestational age, history of spontaneous preterm birth (< 37 weeks), symptoms of preterm labor, and delivery year. Data from 339 women were analyzed, 113 with dynamic cervical shortening comprised the study group, and two groups with 113 women each, matched for the minimal and maximal cervical lengths measured comprised the control groups. Rates of spontaneous preterm birth rate at < 37 weeks (32.7% vs. 15.9%; OR [95% CI]: 2.60 (1.36, 4.87), P=0.004) and < 35 weeks (15.9% vs. 5.3%; OR [95% CI]: 3.38 (1.29, 8.86), P=0.013) were significantly higher among those with dynamic cervix than among the control group matched for the maximal cervical length, and comparable to the control group matched for the minimal cervical length. The negative predictive values of cervical length for preterm birth occurrence at various cut-off values were lower in those with dynamic cervix. In those with dynamic cervical shortening and initial cervical length ≥25 mm, rates of spontaneous preterm birth < 37 weeks (32.9% vs. 14.4%, OR [95% CI]: 2.92 (1.46, 5.81), P=0.002) and < 35 weeks (19.5% vs. 5.1%, OR [95% CI]: 4.52 (1.69, 12.20), P=0.003) were significantly higher as compared with those with cervical length ≥25 mm in the two control groups. The minimal cervical length measured should be used in order to guide patient management when dynamic cervix is noted. In the setting of dynamic cervical change, the value of cervical length as a negative predictor of preterm birth is limited. Further studies are warranted to identify the optimal treatment strategy among women with real time sonographic cervical shortening.

P29.09: The use of long‐term indomethacin stabilises cervical length in twin pregnancies

To determine if the use of early onset (less than 25 weeks) long-term indomethacin therapy (greater than 48 hours) (LIT) stabilises the cervical length (CL) in dichorionic-diamniotic twin gestations (DCDA-T) that are complicated by a short cervix. DCDA-T pregnancies with short CL (less than 30mm) after 18 weeks were identified. Serial CL measurements, other treatments (17 OH-P, vaginal progesterone, nifedipine) and outcomes were collected. Patients with cervical cerclage were excluded. The degree of cervical shortening from initial to last examination was compared in patients with a short CL and women with a normal CL at same gestational age (GA). Longitudinal analysis of the change in CL was modelled using mixed-model regression analysis and predicted values were compared using comparisons of the slope analysis. Out of 63 patients, 25 (40%) received LIT. The GA at initial ultrasound was similar between groups (P=0.6). There were no differences between the two groups regarding history of preterm birth and use of progesterone or nifedipine. The initial and last CLs were shorter in LIT group (24mm vs 43mm and 10mm vs 36.5mm). The average duration of indocin use was 49 days. A total of 255 (LIT=165, Normal CL=90) longitudinal CL examinations were used for mixed-model regression analysis. CL improved or did not change in LIT group (0-0.6mm/week)(CL= -0.0003GA2 + 0.7292GA - 0.0458, R2=0.046). However, in normal CL group, CL declined by 0.06-1.9mm/w (CL=0.091GA2 - 5.98GA+126.14, R2=0.21)(p<0.001). There were no reportable antenatal side effects. Early onset long-term indomethacin therapy in DCDA-T with a short cervix provides an alternative treatment modality to stabilise cervix.

Does Intramuscular Progesterone Help Women With Prior Preterm Birth Screened for Ultrasound-Indicated Cerclage? [25K

INTRODUCTION: Weekly intramuscular 17α-hydroxyprogesterone caproate (17P) is endorsed by the American College of Obstetricians and Gynecologists for recurrent preterm birth (PTB) prevention. Cerclage is indicated in patients with prior PTB and a midtrimester cervical length (CL) less than 25 mm. We aimed to assess if these two preventive strategies, when combined, confer additive benefit in prolonging gestation. METHODS: Retrospective cohort of all singletons delivered at a single center that underwent CL screening from 2011 to 2016 for prior PTB. Exposure was any 17P use. Primary outcome was gestational age (GA) at delivery. Secondary outcomes included cerclage, preterm labor (PTL) admission, and preterm premature rupture of membranes (PPROM). ANCOVA was used to assess the relationship between 17P and delivery GA, controlling for cerclage, initial CL, number of prior PTB, and GA of earliest prior PTB. RESULTS: Of 409 patients who underwent CL screening, 293 received 17P (group 17P), and 116 did not. Groups did not differ by age, race, BMI, payer, number of prior PTB, or initial CL. GA of earliest prior PTB was lower in group 17P (27.4 vs 29.9 weeks; P &lt; .001). Delivery GA occurred earlier in group 17P (35.7 vs 37.2 weeks; P=.002). Group 17P also had higher rates of PPROM (22.2% vs 11.2%; P=.011), PTL admission (42% vs 25%; P=.001), and cerclage (18.1% vs 5.2%; P &lt; .001). After controlling for confounders, delivery GA remained significantly lower in group 17P (34.9 vs 35.9 weeks; P=.027). CONCLUSION: In a population with prior PTB followed with CL screening and ultrasound-indicated cerclage, 17P did not prolong gestation.

Does 17a-Hydroxyprogesterone Caproate for Preterm Birth Prevention Affect Midtrimester Cervical Length? [37F

INTRODUCTION: Weekly intramuscular 17a-hydroxyprogesterone caproate (17P) is endorsed by the American College of Obstetricians and Gynecologists for recurrent preterm birth (PTB) prevention. Cerclage is indicated in patients with prior PTB and a midtrimester cervical length (CL) less than 25 mm. While 17P and CL screening are used concurrently in this population, 17P’s effect on CL is unclear. As such, we aimed to investigate the effect of 17P on midtrimester CL in patients with prior PTB. METHODS: Retrospective cohort of all singletons delivered at a single center that underwent CL screening from 2011 to 2016 for prior PTB. Exposure was defined as at least one dose of 17P administered prior to the last measured CL. Primary outcome was shortest observed CL. Secondary outcomes included rate of CL shortening to less than 25 mm and cerclage. ANCOVA was used to assess the relationship between 17P and shortest observed CL, controlling for significant covariates. RESULTS: Of 409 women who had CL screening, 211 received and 198 did not receive 17P prior to the last CL. Exposed and unexposed groups differed by initial CL (38.3 vs 36.0 mm, respectively; P &lt; .005) and gestational age of earliest prior PTB (27.1 vs 29.2 weeks, respectively; P &lt; .001). Rates of CL shortening to less than 25 mm (P = .93) and cerclage (P = .471) were similar. After controlling for confounders, shortest observed CL was significantly shorter in those who received 17P prior to the last CL (30.2 vs 32.7 mm; P &lt; .001). CONCLUSION: 17P does not prevent midtrimester CL shortening in patients with prior PTB.

The Use of Long-Term Indomethacin Stabilizes Cervical Length in Twin Pregnancies [7Q

INTRODUCTION: To determine if the use of early onset (less than 25 weeks) long-term indomethacin therapy (greater than 48 hours) (LIT) stabilizes the cervical length (CL) in dichorionic-diamniotic twin gestations (DCDA-T) that are complicated by a short cervix. METHODS: DCDA-T pregnancies with short CL (less than 30 mm) after 18 weeks were identified. Serial CL measurements, other treatments (17 OH-P, vaginal progesterone) and outcomes were collected. Patients with cervical cerclage were excluded. The degree of cervical shortening from initial to last examination was compared in patients with a short CL and women with a normal CL at same gestational age (GA). Longitudinal analysis of the change in CL was modeled using mixed-model regression analysis and predicted values were compared using comparisons of the slope analysis. RESULTS: Out of 77 patients, 32 (42%) received LIT. The GA at initial ultrasound was similar between groups (P=0.6). Initial and last CLs were shorter in LIT group (21 mm vs 43 mm and 11.5 mm vs 36 mm) (P &lt; .0001 for both). A total of 434 (LIT=191, Normal CL=243) longitudinal CL examinations were used for mixed-model regression analysis. CL improved or did not change in LIT group (0-0.4 mm/week) (CL= 0.0353GA2-1.5458GA+32.399, R2=0.06). However, in normal CL group, CL was declined by 0.8-1.9 mm/w (CL=0.0529GA2-4.1356x+105.25) (P &lt; .00001). There were no reportable antenatal side effects. CONCLUSION: Early onset long-term indomethacin therapy in DCDA-T with a short cervix provides an alternative treatment modality to stabilize cervix.

High Maternal BMI Associated With Cervical Shortening in Women With Short Cervix on Second Trimester Anatomy Scan [27K

INTRODUCTION: Identify variables associated with cervical length (CL) changes in women with a short CL at time of second trimester anatomy scan. METHODS: Retrospective analysis of patients diagnosed with short CL at time of routine anatomy scan, between 16–26 weeks from October, 2012–June, 2015. Short CL was defined as <25 mm in high risk (HR) or <20 mm in low risk (LR) patients. Patients with history of spontaneous preterm delivery or 1+ 2nd trimester spontaneous abortions defined as HR. Change in CL calculated using difference between initial CL and subsequent measurement. Regression analysis performed with stepwise selection of variables, to assess for variables that are predictive of cervical change. RESULTS: 404 (4.6%)/8,732 scanned found to have short CL. Data incomplete for 208 were excluded from the analysis. Mean maternal age 28.7 and mean gestational age at diagnosis 21w1d. Mean Body Mass Index (BMI) 29.7 kg/m2 (14–57) and mean pregnancy weight gain 19.6 lbs (0–54). 25% were HR and 75% LR. The most common interventions were vaginal progesterone (38%) and cerclage (16%), with 40% expectant. Mean change in CL for this cohort between both scans was a decrease by 14 mm. Using regression analysis, BMI was predictive of CL shortening (P=.052). For every 10 BMI points, the cervix shortened by 1.8 mm. CONCLUSION: In this cohort of patients with short CL identified at time of routine anatomy scan, the BMI was predictive of further CL shortening. These results may imply a need for closer CL surveillance in patients with higher BMI who are found to have a short CL.

667: Do clinical characteristics differ amongst women, with different subsets of preterm premature rupture of membranes?

To study clinical characteristic and the time course to delivery in women presenting with premature rupture of membranes (PPROM). This was a prospective observational study in 106 singletons presenting with PPROM between 23- 33 weeks gestation from July 2011 to March 2014. All women had a TV cervical length on admission. We classified our cohort into three retrospectively assigned groups: 1) spontaneous delivery 2) delivered for maternal or fetal indications and 3) induced for GA beyond 34 weeks. The cumulative times to delivery were examined by life table analysis. Demographic and clinical characteristics were compared using chi-square, Fisher’s-Exact and Kolmogorov-Smirnov tests Eighty one delivered spontaneously. Fifteen women were delivered in group 2 with indications including non-reassuring fetal status (n=5), placental abruption (n=3), cord prolapse (n=3), clinical chorioamnionitis (n=3) and preeclampsia (n=1). Ten women delivered in group 3. No significant differences were seen in days from PROM to delivery among three groups (Figure). Demographics were similar between spontaneous labor group vs. combined non-spontaneous groups, except for higher illicit drug use (16.3% vs. 0.0%, p<0.05) and more maternal asthma (18.8% vs. 0.0%, p<0.05) among the spontaneous labor group. In women with spontaneous labor, the median GA at delivery was lower than the median GA of combined groups 2&3 (31.6 weeks and IQR [29.3-33.1] vs. 32.7 weeks [30.6- 34.0]; (p<0.05). The median initial cervical length after admission and [IQR] was shorter in the group 1 compared to combined groups 2&3; (2.14 cm [1.2-3.4] vs. 3.2 cm [2.2-3.6]; p<0.05). In a prospective study of women with PPROM, the group that eventually delivered spontaneously had a higher incidence of illicit drug use and asthma. Also, they were more likely to have a shorter cervical length on initial transvaginal ultrasound.

Predictive Value of Initial Cervical Length for Subsequent Cervical Length Shortening in Women with a Prior Preterm Birth.

The objective of this study was to estimate the predictive value of the initial cervical length (CL) for later CL shortening in women at high risk for recurrent spontaneous preterm birth (SPTB). Materials and We conducted a secondary analysis of a multicenter randomized trial of high-risk women with CL screening scheduled at least every 2 weeks from 16(0/7) to 22(6/7) weeks. Primary outcome was CL < 25 mm or SPTB before follow-up CL; the risk of this outcome was analyzed by initial CL at 16(0/7) to 21(6/7) weeks using multivariable logistic regression and receiver operator curves. A total of 786 women were identified in the parent trial; 197 (25.0%) developed CL shortening < 23 weeks, 3 (0.4%) delivered within 2 weeks of initial CL measurement (< 24 weeks), and 586 (74.6%) maintained CL ≥ 25 mm. The covariate-adjusted receiver operator characteristics curve had moderate predictive value (area under the curve = 0.748) but did not reveal a clinically useful CL cutoff. Evaluation of selected CL cutoffs demonstrated that an initial CL ≥39 mm had the greatest negative predictive value (85.1%). No CL cutoff existed above which there was no CL shortening, although at ≥ 39 mm only two patients (1.1%) shortened within 2 weeks as compared with 32 (7.1%) patients whose initial CL was < 39 mm (p < 0.001). In high-risk patients whose initial CL is ≥ 39 mm, CL shortening or delivery is uncommon in the following 2 weeks. Patients with initial CL above this threshold may require less frequent surveillance.

183: The rate of sonographic cervical shortening and the risk for spontaneous preterm delivery in twins

Transvaginal cervical length (TVCL) measurements in singleton pregnancies identify women at risk for spontaneous preterm delivery (SPTD). Current evidence supports a relationship between a short cervix (CL< 25 mm) and SPTD in twin pregnancies. The relationship between change in serial TVCL and the risk for SPTD in twin pregnancies remains poorly defined. We hypothesized that the rate of TVCL shortening is associated SPTD <34wks in twin pregnancies, regardless of initial cervical length.

PMM.35 Comprehensive Tools in Assessing Risk of Pre-term Labour: History and Cervical Length

BackgroundScreening methods to determine risk for pre-term delivery include robust history taking and cervical length assessment. A cervical length of <15mm has shown to have a 50% risk of preterm...

467: Frequency of cervical length surveillance in high-risk women based on initial cervical length

467: Frequency of cervical length surveillance in high-risk women based on initial cervical length

Cost-effectiveness of transabdominal ultrasound for cervical length screening for preterm birth prevention

Transabdominal ultrasound (TAUS) cervical length (CL) screening has been proposed as an alternative to universal transvaginal screening to identify women at an increased risk of preterm birth. We sought to identify whether and under what circumstances TAUS would be cost-effective. This is a decision analytic model designed to compare an initial TAUS CL screening approach with universal transvaginal screening in a hypothetical cohort of women with a singleton pregnancy. Cost, probability, and utility estimates were derived from the existing literature. Under baseline assumptions, universal transvaginal was the dominant strategy. In comparison to TAUS, universal transvaginal CL screening reduced preterm birth by 0.03%, reduced costs by $1.2 million and increased quality-adjusted life years by 70 per 100,000 women. Although robust to many changes in many estimates, the model was sensitive to the cost of a transvaginal ultrasound, the prevalence of a short cervix and the test characteristics (ie, sensitivity and specificity) of a TAUS screening examination for short CL. Compared with an initial TAUS screen, universal transvaginal ultrasound was a more cost-effective strategy under most assumptions. Optimizing TAUS testing characteristics or applying a transabdominal screening strategy in lower risk populations may yield an initial TAUS to be cost-effective.