Data from: Preterm birth prevention post-conization: a model of cervical length screening with targeted cerclage

Women with a history of excisional treatment (conization) for cervical
intra-epithelial neoplasia (CIN) are at increased risk of preterm birth,
perinatal morbidity and mortality in subsequent pregnancy. We aimed to
develop a screening model to effectively differentiate pregnancies
post-conization into low- and high-risk for preterm birth, and to evaluate
the impact of suture material on the efficacy of ultrasound indicated
cervical cerclage. We analysed longitudinal cervical length (CL) data from
725 pregnant women post-conization attending preterm surveillance clinics
at three London university Hospitals over a ten year period (2004–2014).
Rates of preterm birth <37 weeks after targeted cerclage for
CL<25mm were compared with local and national background rates and
expected rates for this cohort. Rates for cerclage using monofilament or
braided suture material were also compared. Of 725 women post-conization
13.5% (98/725) received an ultrasound indicated cerclage and 9.7% (70/725)
delivered prematurely, <37weeks; 24.5% (24/98) of these despite
insertion of cerclage. The preterm birth rate was lower for those that had
monofilament (9/60, 15%) versus braided (15/38, 40%) cerclage (RR 0.7, 95%
CI 0.54 to 0.94, P = 0.008). Accuracy parameters of interval reduction in
CL between longitudinal second trimester screenings were calculated to
identify women at low risk of preterm birth, who could safely discontinue
surveillance. A reduction of CL <10% between screening timepoints
predicts term birth, >37weeks. Our triage model enables timely
discharge of low risk women, eliminating 36% of unnecessary follow-up CL
scans. We demonstrate that preterm birth in women post-conization may be
reduced by targeted cervical cerclage. Cerclage efficacy is however suture
material-dependant: monofilament is preferable to braided suture. The
introduction of triage prediction models has the potential to reduce the
number of unnecessary CL scan for women at low risk of preterm birth.

有宫颈上皮内瘤变（CIN）锥切术（conization）史的女性在后续妊娠中早产、围产期发病率及死亡率的风险升高。本研究旨在开发一种筛查模型，以有效区分锥切术后妊娠的早产低风险与高风险人群，并评估缝合材料对超声引导宫颈环扎术（cervical cerclage）疗效的影响。我们分析了2004–2014年十年间伦敦三所大学医院早产监测门诊的725例锥切术后孕妇的纵向宫颈长度（CL）数据。将宫颈长度<25mm时行靶向环扎术后的早产（<37周）发生率与当地及全国背景发生率、该队列预期发生率进行比较；同时比较单丝与编织缝线材料的环扎术效果。在725例锥切术后女性中，13.5%（98/725）接受了超声引导环扎术，9.7%（70/725）发生早产（<37周），其中24.5%（24/98）为环扎术后仍早产。单丝缝线环扎组早产率（9/60，15%）低于编织缝线组（15/38，40%），相对风险（RR）为0.7，95%置信区间（CI）0.54–0.94，P=0.008。通过计算孕中期纵向筛查间宫颈长度的区间减少率参数，识别早产低风险女性以安全终止监测：筛查时间点间宫颈长度减少<10%可预测足月分娩（>37周）。我们的分诊模型能及时让低风险女性出院，减少36%不必要的后续宫颈长度扫描。研究表明，靶向宫颈环扎术可降低锥切术后女性的早产率，但环扎术疗效依赖于缝合材料：单丝缝线优于编织缝线。引入分诊预测模型有望减少早产低风险女性的不必要宫颈长度扫描次数。