Division of Clinical Research, Department of Obstetrics and Gynecology, Washington University in St. Louis School of Medicine, St. Louis, Missouri.
Obstet Gynecol. 2014 Mar;123(3):521-526. doi: 10.1097/AOG.0000000000000131.
Studies using contemporary populations and modern statistical methods have redefined our understanding of cervical dilation in labor. However, modern norms for fetal descent in labor have not been developed. We sought to estimate norms for fetal descent and estimate the expected fetal station for given cervical dilations.
A retrospective cohort study of consecutive-term, vertex singletons who delivered vaginally. Detailed history, labor, and delivery information, including cervical examinations, were collected. A repeated-measures analysis was used to construct average descent curves. Interval-censored regression was used to estimate duration of labor between levels of station and to estimate the median station at a given dilation. Each analysis was stratified by parity and labor type (spontaneous compared with induced or augmented).
Of 4,618 consecutive-term spontaneous vaginal deliveries, 1,526 (33%) were nulliparous. Sixty-one percent were augmented or induced. Multiparous women had faster fetal descent at all stations except from +2 to +3 station. The median time to descend from one station point to another ranged from 0.1 to 1.6 hours, but the 95th percentiles encompassed over 12 hours at the same high-station among nulliparous women who achieved vaginal delivery. Fetal descent was more rapid in women who labored spontaneously without augmentation. Multiparous women tended to have a higher station than nulliparous women until late in the first stage.
Multiparous women and women who are not augmented or induced have faster fetal descent. There is wide variation in the expected station by increments of dilation. However, 95% of women have a fetal station of 0 or lower at complete cervical dilation.
使用当代人群和现代统计方法的研究重新定义了我们对分娩时宫颈扩张的理解。然而，尚未制定分娩时胎儿下降的现代标准。我们试图估计胎儿下降的正常值，并估计给定宫颈扩张的预期胎儿位置。
这是一项连续足月、头位单胎阴道分娩的回顾性队列研究。收集详细的病史、分娩和分娩信息，包括宫颈检查。采用重复测量分析构建平均下降曲线。间隔censored 回归用于估计不同胎方位之间的产程时间，并估计在给定扩张程度时的中位数胎方位。每次分析均按产次和分娩类型（自然分娩与引产或催产）分层。
在 4618 例连续足月自然分娩中，1526 例（33%）为初产妇。61%为引产或催产。除了从+2 到+3 位，多产妇在所有部位的胎儿下降速度都更快。从一个部位点下降到另一个部位点的中位数时间范围为 0.1 至 1.6 小时，但在初产妇中，在同一高位分娩时，95%的时间超过 12 小时。未接受催产或引产的自然分娩妇女的胎儿下降速度更快。多产妇的胎方位通常高于初产妇，直到第一产程后期。
多产妇和未接受催产或引产的产妇胎儿下降速度更快。宫颈扩张每增加一度，预期胎方位的差异很大。然而，95%的产妇在宫颈完全扩张时胎儿的胎方位为 0 或更低。
