Predicting spontaneous preterm birth in asymptomatic high-risk women with cervical cerclage

OBJECTIVE

To determine the performance of the predictive markers of spontaneous preterm birth, cervicovaginal quantitative fetal fibronectin (fFN) and cervical length, in asymptomatic high-risk women with transabdominal, history-indicated or ultrasound-indicated cervical cerclage.

METHODS

This was a secondary analysis of a prospective cohort of asymptomatic high-risk women with cervical cerclage and no other prophylactic intervention (including progesterone), who attended the preterm birth clinic at a central London teaching hospital between October 2010 and September 2016. Women had either transabdominal cerclage, placed prior to conception, history-indicated cerclage, placed before 14 weeks' gestation, or ultrasound-indicated cerclage for a short cervix (< 25 mm), placed before 24 weeks. All women underwent serial cervical length assessment on transvaginal ultrasound in the second trimester (16-28 weeks), and quantitative fFN testing from 18 weeks onward. Test performance was analyzed for the prediction of spontaneous preterm birth before 30 weeks (cerclage failure), 34 weeks and 37 weeks, using receiver-operating-characteristics (ROC)-curve analysis.

RESULTS

Overall, 181 women were included in the analysis. Cervical length and fFN were strong predictors of spontaneous preterm birth before 30 weeks in women with cerclage, with areas under the ROC curve (AUC) of 0.86 (95% CI, 0.79-0.94) and 0.84 (95% CI, 0.75-0.92), respectively. Cervical length was a better predictor of preterm birth before 30 weeks in women with history-indicated compared to those with ultrasound-indicated cerclage, although both showed clinical utility (AUC, 0.96 (95% CI, 0.91-1.00) vs 0.79 (95% CI, 0.66-0.91); P = 0.01). Quantitative fFN was a strong predictor of spontaneous preterm birth before 30 weeks in women with history-indicated cerclage (AUC, 0.91 (95% CI, 0.75-1.00)) and retained clinical utility in those with ultrasound-indicated cerclage (AUC, 0.76 (95% CI, 0.64-0.89)). There were no spontaneous deliveries before 34 weeks in women with a transabdominal cerclage, so AUC was not calculated. Delivery was delayed significantly in this group (P < 0.01).

CONCLUSIONS

Cervical length and quantitative fFN retain clinical utility for the prediction of spontaneous preterm birth in women with cervical cerclage, and prediction is best in women with a history-indicated stitch. These tests can be relied upon to discriminate risk and have utility when planning clinical management with regard to treatment failure. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Development and validation of predictive models for QUiPP App v.2: tool for predicting preterm birth in asymptomatic high-risk women

OBJECTIVES

Accurate mid-pregnancy prediction of spontaneous preterm birth (sPTB) is essential to ensure appropriate surveillance of high-risk women. Advancing the QUiPP App prototype, QUiPP App v.2 aimed to provide individualized risk of delivery based on cervical length (CL), quantitative fetal fibronectin (qfFN) or both tests combined, taking into account further risk factors, such as multiple pregnancy. Here we report development of the QUiPP App v.2 predictive models for use in asymptomatic high-risk women, and validation using a distinct dataset in order to confirm the accuracy and transportability of the QUiPP App, overall and within specific clinically relevant time frames.

METHODS

This was a prospective secondary analysis of data of asymptomatic women at high risk of sPTB recruited in 13 UK preterm birth clinics. Women were offered longitudinal qfFN testing every 2-4 weeks and/or transvaginal ultrasound CL measurement between 18 + 0 and 36 + 6 weeks' gestation. A total of 1803 women (3878 visits) were included in the training set and 904 women (1400 visits) in the validation set. Prediction models were created based on the training set for use in three groups: patients with risk factors for sPTB and CL measurement alone, with risk factors for sPTB and qfFN measurement alone, and those with risk factors for sPTB and both CL and qfFN measurements. Survival analysis was used to identify the significant predictors of sPTB, and parametric structures for survival models were compared and the best selected. The estimated overall probability of delivery before six clinically important time points (< 30, < 34 and < 37 weeks' gestation and within 1, 2 and 4 weeks after testing) was calculated for each woman and analyzed as a predictive test for the actual occurrence of each event. This allowed receiver-operating-characteristics curves to be plotted, and areas under the curve (AUC) to be calculated. Calibration was performed to measure the agreement between expected and observed outcomes.

RESULTS

All three algorithms demonstrated high accuracy for the prediction of sPTB at < 30, < 34 and < 37 weeks' gestation and within 1, 2 and 4 weeks of testing, with AUCs between 0.75 and 0.90 for the use of qfFN and CL combined, between 0.68 and 0.90 for qfFN alone, and between 0.71 and 0.87 for CL alone. The differences between the three algorithms were not statistically significant. Calibration confirmed no significant differences between expected and observed rates of sPTB within 4 weeks and a slight overestimation of risk with the use of CL measurement between 22 + 0 and 25 + 6 weeks' gestation.

CONCLUSIONS

The QUiPP App v.2 is a highly accurate prediction tool for sPTB that is based on a unique combination of biomarkers, symptoms and statistical algorithms. It can be used reliably in the context of communicating to patients the risk of sPTB. Whilst further work is required to determine its role in identifying women requiring prophylactic interventions, it is a reliable and convenient screening tool for planning follow-up or hospitalization for high-risk women. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Ability of a preterm surveillance clinic to triage risk of preterm birth: a prospective cohort study

OBJECTIVE

To identify whether preterm surveillance clinics (PSCs) risk-stratify high-risk women accurately by comparing outcomes of those admitted to hospital on the basis of asymptomatic testing with those not admitted.

METHODS

We performed a subanalysis from a larger prospective cohort study on sonographic cervical length, quantitative fetal fibronectin (qfFN) and risk of spontaneous preterm birth. We identified 1130 asymptomatic singleton pregnancies at high risk of preterm birth, screened between 23 and 28 weeks of gestation at a PSC in a tertiary hospital in London, UK. Gestational age at delivery, the proportion of preterm births that delivered < 30 weeks and neonatal outcomes were compared between women admitted electively when asymptomatic as a consequence of screening-test results and those who were not routinely admitted.

RESULTS

In total, 66 (6%) women attending the PSC were admitted to hospital following asymptomatic screening (inpatient group). The mean gestational age at delivery for those not admitted electively (outpatient group) was at term and was significantly higher than that of those admitted from PSC (38.4 vs 31.2 weeks; P < 0.0001). Preterm birth < 30 weeks' gestation was rare in the outpatient group relative to those admitted (1.32% vs 36.4%; P < 0.0001). Neonatal mortality was 0.188% in the outpatient group compared with 4.55% in those admitted electively (P < 0.0001). The incidence of other complications such as neonatal death, 5-min Apgar score < 7, special care baby unit/neonatal intensive care unit admission, respiratory distress syndrome, intraventricular hemorrhage and low birth weight were significantly lower in those managed as outpatients than in those admitted electively.

CONCLUSION

PSCs measuring cervical length and qfFN accurately triage asymptomatic high-risk pregnant women, enabling those at highest risk of adverse outcome to be identified for elective admission to hospital and appropriate management. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Development and validation of a tool incorporating quantitative fetal fibronectin to predict spontaneous preterm birth in symptomatic women

OBJECTIVE

To develop a reliable and validated tool for prediction of spontaneous preterm birth (sPTB) in symptomatic women that incorporates quantitative measurements of fetal fibronectin (qfFN) and other relevant risk factors.

METHODS

Data were analyzed that had been collected prospectively from 382 women who presented at an emergency assessment unit between 22 + 0 and 35 + 6 weeks' gestation with symptoms of preterm labor. Clinicians were blinded to qfFN although they were aware of qualitative fFN results. Parametric survival models for sPTB, with time-updated covariates, were developed for combinations of predictors and the best was selected using the Akaike and Bayesian information criteria. The model was developed on the first 190 consecutive women and validated on the subsequent 192. The estimated probability of delivery before 30, 34 or 37 weeks' gestation and within 2 or 4 weeks of testing was calculated for each patient and was compared to actual event rates. Predictive statistics were calculated to compare training and validation sets.

RESULTS

The final model that was selected used qfFN and previous sPTB/preterm prelabor rupture of membranes (PPROM) as predictors. Predictive statistics were similar for training and validation sets and there was good agreement between expected and observed sPTB for all outcomes. Areas under the receiver-operating characteristics curves ranged from 0.77 to 0.88, indicating accurate prediction across all five delivery outcomes.

CONCLUSIONS

sPTB in symptomatic women can be predicted accurately using a model combining qfFN and previous sPTB/PPROM. Clinicians can use this model, which has been incorporated into an App (QUiPP), to determine accurately a woman's risk of sPTB and potentially tailor management decisions appropriately.

Development and validation of a tool incorporating cervical length and quantitative fetal fibronectin to predict spontaneous preterm birth in asymptomatic high-risk women

OBJECTIVE

To develop a predictive tool for spontaneous preterm birth (sPTB) in asymptomatic high-risk women that includes quantification of fetal fibronectin (fFN) along with cervical length (CL) measurement and other clinical factors.

METHODS

Data were analyzed that had been collected prospectively from 1249 women at high risk for sPTB attending preterm surveillance clinics. Clinicians were blinded to quantitative measurements of fFN (qfFN), although they were aware of qualitative fFN results. Parametric survival models for sPTB, with time-updated covariates, were developed and the best was selected using the Akaike and Bayesian information criteria. The model was developed on the first 624 consecutive women and validated on the subsequent 625. Fractional polynomials were used to accommodate possible non-linear effects of qfFN and CL. The estimated probability of delivery before 30, 34 or 37 weeks' gestation and within 2 or 4 weeks of testing was calculated for each patient and analyzed as a predictive test for the actual occurrence of each event. Predictive statistics were calculated to compare training and validation sets.

RESULTS

The final model that was selected used a log-normal survival curve with CL, √qfFN and previous sPTB/preterm prelabor rupture of membranes as predictors. Predictive statistics were similar for training and validation sets. Areas under the receiver-operating characteristics curves ranged from 0.77 to 0.99, indicating accurate prediction across all five delivery outcomes.

CONCLUSIONS

sPTB in high-risk asymptomatic women can be predicted accurately using a model combining qfFN and CL, which supersedes the single-threshold fFN test, demographic information and obstetric history. This algorithm has been incorporated into an App (QUiPP) for widespread use.