Table 1.
Patient characteristics for women that delivered at term without cerclage (Group 1) and women that had cerclage or delivered prematurely (Group 2).
Table 2.
Preterm birth rates: A in the UK; B in the local population (three study units); C estimated in women post-cervical treatment based on UK rates; D in this study cohort.
Fig 1.
Gestation at delivery in women with an ultrasound-indicated cerclage for CL <25mm before 24weeks: a comparison of suture material braided versus monofilament.
Preterm birth <37weeks was significantly higher (P = 0.08) in women with braided cerclages, compared to monofilament cerclages. This is difference is most notable among those delivering late preterm birth (34-37weeks).
Table 3.
Neonatal outcome as a function of cerclage suture material.
Fig 2.
Mean difference in CL (mean % Δ CL) between time-points A: 13+0–15+6 weeks, B: 16+0–18+6 weeks, C: 20+0–22+6 weeks (A-B, B-C, and A-C) according to delivery outcome and cerclage insertion. In women receiving a cerclage, mean CL started above 25mm at timepoint A, and went on to shorten, most significantly at timepoint C. The greatest difference in CL is observed between timepoints B-C and A-C in those that received a cerclage and went on to deliver preterm <37weeks, followed by term delivery with a cerclage. (% ΔCL = percentage change in CL (mm) between screening time points; PTB = preterm birth <37 weeks; Screening time points = A: 13+0–15+6 weeks, B: 16+0–18+6 weeks, C: 20+0–22+6 weeks; SD = standard deviation; Term = birth >37 weeks; W = weeks).
Table 4.
Mean CL (mm)(SD) at screening time-points A, B, C and mean percentage ΔCL (SD) between screening time-points A-B, B-C, and A-C for Group 1 and 2.
Table 5.
Sensitivity, specificity, likelihood ratios, and positive and negative predictive values for cerclage intervention and/or preterm birth <37 weeks, for screening time-points A, B and C, and percentage difference in CL between screening time-points A, B and C.
Fig 3.
Triage Screening Model for pregnancies post excisional cervical treatment for the prevention of preterm birth <37weeks.
A triage screening model was developed using decision tree analyses to determine optimum thresholds of CL and % change in CL between screening timepoints A (13+0–15+6 weeks), B (16+0–18+6 weeks) and C (20+0–22+6 weeks), to ensure appropriate allocation of resources. This model identifies pregnancies at low-risk of preterm birth enabling safe and timely discharged from cervical length surveillance (green dot). Similarly early identification of high-risk pregnancies allows for timely cerclage intervention (red dot). Serial CL surveillance can therefore reserved for pregnancies considered at intermediate risk, requiring further observation. CL = cervical length (mm); CLAB% = percentage change in CL (mm) between screening time points; w = weeks.