Vaginal Ultrasound Cerclage Trial

阴道超声环扎术是一项多中心、随机的临床试验，旨在确定环扎术(在宫颈周围放置一种荷包缝线)预防妊娠35周前自发早产的效果。我们建议研究具有反复自然早产风险的妇女(那些在怀孕17-32周时有过自然分娩经历的妇女)，以及那些基于中期超声发现宫颈长度为25 mm而增加风险的妇女。一个由7个围产期中心组成的财团将识别大约1000名在怀孕17-32周时有自然早产史的妇女，这些中心在进行临床试验方面的专业知识在全国范围内得到认可。这些妇女将接受两周一次的阴道超声检查，从16-18周开始，到22周结束。根据我们的试点数据，这些妇女中大约有三分之一的人将拥有或发育宫颈25 mm，并有资格随机接受环扎术或不环扎组(对照组)。这项试验的疗效和样本量建议是基于文献中的许多报告，特别是基于多中心NICHD母胎医学单位网络对阴道超声数据进行的两项前瞻性观察研究。将解决以下具体目标：1.通过连续中期阴道超声评估，确定放置宫颈环扎术是否会减少有早期自然早产且宫颈长度为25 mm的妇女在35周之前的自然分娩。2.在妊娠16-22周的患者群体中确定宫颈环扎的安全性。(辅助目标)测量阴道pH值并进行阴道菌群革兰氏染色，收集和存储母体血清和宫颈阴道液，以供以后分析选定的标志物以预测早产，以便：A.将这些标志物与环扎失败的成功相关；2.进一步确定早期自发早产的可能机制。

The Vaginal Ultrasound Cerclage Trial is a multicenter, randomized clinical trial, designed to determine the efficacy of cerclage (a purse- string suture placed around the uterine cervix) for the prevention of spontaneous preterm birth prior to 35 weeks' gestation. We propose to study women at significant risk for recurrent spontaneous preterm birth (those with a prior spontaneous birth at 17-32 weeks' gestation) and who also have an increased risk based on midtrimester ultrasonographic findings of a cervical length <25mm. A consortium of 7 perinatal centers, recognized nationally for their expertise in the conduct of clinical trials, will identify approximately 1000 women with a history of a spontaneous preterm birth at 17-32 weeks' gestation. These women will undergo biweekly vaginal sonography beginning at 16-18 weeks, and ending by 22 weeks. Based on our pilot data, approximately one- third of these women will either have or develop a cervix <25mm and be eligible for randomization to cerclage or no cerclage (control group). The proposed efficacy and sample size for this trial is based on many reports in the literature and particularly on two prospective observational studies of vaginal ultrasonographic data from the multicenter NICHD Maternal Fetal Medicine Units Network. The following specific aims will be addressed: 1. To determine if placement of a cervical cerclage reduces spontaneous birth prior to 35 weeks' gestation in women with a prior early spontaneous preterm birth and with a cervix <25mm in length, as determined by serial midtrimester vaginal sonographic evaluation. 2. To determine the safety of cervical cerclage placement at 16-22 weeks' gestation in the patient population described in Aim#1. 3. (Ancillary Aim) To measure vaginal pH and perform Gram stains of vaginal flora and to collect and store maternal serum and cervicovaginal fluid for later analysis of selected markers to predict preterm delivery in order to: A. correlate these markers with the success of failure of cerclage B. further define possible mechanisms of early spontaneous preterm birth.