Abstract：
An accurate transvaginal ultrasound cervical length is paramount to obtain the best prediction for preterm birth. Transvaginal ultrasound cervical length should be optimally obtained when a lower uterine segment contraction is not seen. For universal transvaginal ultrasound cervical length screening at approximately 20 weeks of gestation, the options are to do the transvaginal ultrasound soon after bladder void (lower uterine segment contractions present in 16%-43% of this approach) or to wait until the end of the anatomy scan (ideally within 30 minutes after bladder voiding) to decrease the chance of a lower uterine segment contraction. If the lower uterine segment contraction persists even after waiting up to 20 minutes or more, only the true transvaginal ultrasound cervical length should be reported. In particular, in patients with a previous spontaneous preterm birth, if the lower uterine segment contraction persists, the transvaginal ultrasound cervical length can be repeated in ≤7 days even in the presence of a normal (>25 mm) cervical length. Similar to a blood pressure cuff that must be of the right size for proper blood pressure measurement and a glucometer that must be properly calibrated, screening with transvaginal ultrasound cervical length should only be performed following a proper and standardized technique, including avoiding as much as feasible the presence of lower uterine segment contractions.
摘要：
准确的经阴道超声（TVU）宫颈长度（CL）对于获得早产（PTB）的最佳预测至关重要。当没有看到子宫下段（LUS）收缩（CTX）时，应最佳地获得TVUCL。对于大约20周的通用TVUCL筛查，选择是在膀胱空后立即进行TVU（这种方法的16-43％存在LUSCTX），或等待直到解剖扫描结束（理想情况下在膀胱排尿后30分钟内），以减少LUSCTX的机会。如果LUSCTX在等待20分钟或更长时间后仍然存在，仅应报告真实的TVUCL。特别是在先前有自发性PTB的患者中，如果LUSCTX持续存在,即使存在正常（>25mm）CL，TVUCL也可以在7天或更短时间内重复。就像血压袖带必须具有合适的尺寸以进行适当的BP测量一样，血糖仪必须正确校准，使用TVUCL进行筛查只能遵循适当和标准化的技术，包括尽可能避免LUSCTX的存在。
