Ahmad A, Webb S S, Early B, Sitch A, Khan K, Macarthur C
Birmingham Women's NHS Foundation Trust, Birmingham, UK; Public Health, Epidemiology & Biostatistics, University of Birmingham, Edgbaston, UK.
Ultrasound Obstet Gynecol. 2014 Feb;43(2):176-82. doi: 10.1002/uog.13189.
To determine the association between fetal position at onset of labor and mode of delivery, specifically left occipito-anterior (LOA) fetal position and spontaneous vaginal delivery (SVD).
All nulliparous women who were booked at the Birmingham Women's NHS Foundation Trust over an 18-month period from April 2007 to September 2008 with a singleton live fetus without structural anomalies at term gestation were invited to take part in the study. Women recruited to the study underwent a transabdominal ultrasound scan to determine fetal occiput position at the onset of labor. They were then followed up until birth to determine outcome. The primary outcome measure was mode of delivery, categorized into SVD, instrumental delivery and Cesarean section.
Of 1647 eligible women, 1250 had valid scans at onset of labor; 155 of the 1250 (12.4%) had fetuses in the LOA position. Analysis showed no evidence of difference in odds ratio (OR) of SVD for fetuses in the LOA position compared with all other positions (OR 0.864 (95% CI, 0.617-1.209); P = 0.394). No difference remained with adjustment for confounding effects of variables known to influence mode of delivery (OR 0.837 (95% CI, 0.551-1.272); P = 0.405). No other occipital position showed significant association with SVD. There was no evidence of the LOA position being associated with Cesarean section, ventouse or forceps delivery.
There is no evidence of an association between the fetal LOA position at onset of labor and SVD. This finding challenges the conventional theory that LOA is the optimum fetal position at onset of labor, and suggests that antenatal practices encouraging adoption of the LOA position through maternal posturing are unnecessary.
确定分娩开始时的胎儿位置与分娩方式之间的关联，特别是左枕前（LOA）胎儿位置与自然阴道分娩（SVD）之间的关联。
邀请2007年4月至2008年9月期间在伯明翰妇女国民保健服务基金会信托机构登记的所有未生育妇女参与研究，这些妇女单胎足月活胎且无结构异常。参与研究的妇女接受经腹超声扫描以确定分娩开始时的胎儿枕骨位置。然后对她们进行随访直至分娩以确定结局。主要结局指标是分娩方式，分为自然阴道分娩、器械助产和剖宫产。
在1647名符合条件的妇女中，1250名在分娩开始时有有效扫描结果；1250名中的155名（12.4%）胎儿为左枕前位。分析表明，与所有其他位置相比，左枕前位胎儿自然阴道分娩的优势比（OR）没有差异（OR 0.864（95%可信区间，0.617 - 1.209）；P = 0.394）。在对已知影响分娩方式的变量的混杂效应进行调整后，差异仍然不存在（OR 0.837（95%可信区间，0.551 - 1.272）；P = 0.405）。没有其他枕骨位置与自然阴道分娩有显著关联。没有证据表明左枕前位与剖宫产、真空吸引助产或产钳助产有关。
没有证据表明分娩开始时胎儿左枕前位与自然阴道分娩之间存在关联。这一发现挑战了传统理论，即左枕前位是分娩开始时的最佳胎儿位置，并表明通过产妇体位鼓励采用左枕前位的产前措施是不必要的。
