Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, Canada; PeriGen, Cranbury, NJ, and Westmount, Quebec, Canada.
Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Quebec, Canada.
Am J Obstet Gynecol. 2016 Mar;214(3):360.e1-6. doi: 10.1016/j.ajog.2015.10.005. Epub 2015 Oct 22.
High station at specific points in the first stage of labor, such as a floating head on admission, or at 4-cm dilation or when arrest of dilation occurs, is associated with higher rates of failure to deliver vaginally. Therefore it could be useful to know if station is within an expected range at a given dilation during first stage. Arrest of descent disorders have been defined thus far on criteria applicable in the second stage. Statistical modeling is an attractive methodology to characterize the relationship between station and dilation because the resulting mathematical expressions could be used as a reference for comparison in the future. In addition, they can be used to produce a finely graded assessment of descent using numerical terms such as percentile rankings. A 2-step approach to potentially improving the assessment of station could be to develop a statistical model that describes the general relationship between station and dilation in the first stage of uncomplicated births and then determine if such a model would have identified births with complications related to poor labor progress. Given the complex nature of labor data, especially the imprecision of dilation and station measurement, it is not immediately evident that such a model is identifiable or what its precision would be.
We sought to characterize in mathematical terms the relationship of station to dilation during the first stage of labor for nulliparous and multiparous women with spontaneous vaginal births.
This retrospective cohort study included 28,121 exams from 5555 women with singleton cephalic presentations at ≥37 weeks' gestation with electronic fetal monitoring tracings, who delivered vaginally without instrumentation and had 5-minute Apgar scores >6 at 2 academic community referral hospitals in 2012 through 2013. Women with a previous cesarean birth were excluded. We used longitudinal statistical techniques suitable to biological data that were irregularly sampled with repeated measures over time.
A linear relationship was observed between station and dilation. For both nulliparous and multiparous women the final model was a linear regression with random effects for intercept and slope and a first-order autoregressive correlation structure. The 5th-95th range of station at any given dilation spanned about 3-4 cm.
Our results demonstrate a general trend of increasing descent of the presenting part as dilation advances during the first stage of labor in women who delivered vaginally without instrumentation. We propose that the mathematical expressions describing this relationship may be valuable in the assessment of first-stage labor progression.
在第一产程的特定阶段（如入院时的浮头，或在 4 厘米扩张或扩张停止时），高位与阴道分娩失败的发生率较高有关。因此，了解在第一产程的特定扩张阶段，胎先露是否处于预期范围内可能会有所帮助。迄今为止，下降障碍的阻滞已根据适用于第二产程的标准来定义。统计建模是一种描述胎先露位置与扩张之间关系的有吸引力的方法，因为由此产生的数学表达式可以用作未来比较的参考。此外，它们可以用于使用数值术语（如百分位数排名）对下降进行精细分级评估。提高胎先露位置评估的潜在两步方法是开发一个描述无并发症分娩第一产程中胎先露位置与扩张之间一般关系的统计模型，然后确定该模型是否可以识别与产程进展不良相关的并发症分娩。考虑到产程数据的复杂性，特别是扩张和胎先露位置测量的不精确性，目前尚不清楚该模型是否可识别或其精度如何。
我们试图用数学术语描述初产妇和经产妇自发性阴道分娩第一产程中胎先露位置与扩张的关系。
这项回顾性队列研究纳入了 2012 年至 2013 年期间在 2 家学术社区转诊医院分娩、无器械助产、电子胎心监护描记、5 分钟 Apgar 评分≥6 的初产妇和经产妇各 5555 例、单胎头位、≥37 孕周的 28121 次检查。排除既往剖宫产分娩的妇女。我们使用适合生物数据的纵向统计技术，这些数据是在时间上具有重复测量的不规则样本。
胎先露位置与扩张之间存在线性关系。对于初产妇和经产妇，最终模型都是带有随机截距和斜率效应的线性回归，以及一阶自回归相关结构。在任何给定的扩张阶段，胎先露的第 5-95 个范围跨度约为 3-4cm。
我们的结果表明，在无器械助产的阴道分娩妇女中，第一产程扩张时胎先露位置呈上升趋势。我们提出，描述这种关系的数学表达式可能对评估第一产程进展有价值。
