Benavides Lorena, Wu Jennifer M, Hundley Andrew F, Ivester Thomas S, Visco Anthony G
Department of Obstetrics and Gynecology, University of North Carolina at Chapel Hill, 27599-7570, USA.
Am J Obstet Gynecol. 2005 May;192(5):1702-6. doi: 10.1016/j.ajog.2004.11.047.
A forceps-assisted vaginal delivery is a well-recognized risk factor for anal sphincter injury. Some studies have shown that occiput posterior (OP) fetal head position is also associated with an increased risk for third- or fourth-degree lacerations. The objective of this study was to assess whether OP position confers an incrementally increased risk for anal sphincter injury above that present with forceps deliveries.
This was a retrospective cohort study of 588 singleton, cephalic, forceps-assisted vaginal deliveries performed at our institution between January 1996 and October 2003. Maternal demographics, labor and delivery characteristics, and neonatal factors were examined. Statistical analysis consisted of univariate statistics, Student t test, chi2, and logistic regression.
The prevalence of occiput anterior (OA) and OP positions was 88.4% and 11.6%, respectively. The groups were similar in age, marital status, body mass index, use of epidural, frequency of inductions, episiotomies, and shoulder dystocias. The OA group had a higher frequency of rotational forceps (16.2% vs 5.9%, P = .03), greater birth weights (3304 +/- 526 g vs 3092 +/- 777 g, P = .004), and a larger percentage of white women (48.8% vs 34.3%, P = .04). Overall, 35% of forceps deliveries resulted in a third- or fourth-degree laceration. Anal sphincter injury occurred significantly more often in the OP group compared with the OA group (51.5% vs 32.9%, P = .003), giving an odds ratio of 2.2 (CI: 1.3-3.6). In a logistic regression model that controlled for occiput posterior position, maternal body mass index, race, length of second stage, episiotomy, birth weight, and rotational forceps, OP head position was 3.1 (CI: 1.6-6.2) times more likely to be associated with anal sphincter injury than OA head position.
Forceps-assisted vaginal deliveries have been associated with a greater risk for anal sphincter injury. Within this population of forceps deliveries, an OP position further increases the risk of third- or fourth-degree lacerations when compared with an OA position.
产钳辅助阴道分娩是公认的肛门括约肌损伤的危险因素。一些研究表明，枕后位（OP）胎儿头部位置也与三度或四度裂伤风险增加有关。本研究的目的是评估枕后位是否会使肛门括约肌损伤风险在产钳分娩基础上进一步增加。
这是一项回顾性队列研究，对1996年1月至2003年10月在我院进行的588例单胎、头位、产钳辅助阴道分娩病例进行分析。研究了产妇人口统计学特征、分娩特征及新生儿因素。统计分析包括单变量统计、Student t检验、卡方检验和逻辑回归分析。
枕前位（OA）和枕后位的发生率分别为88.4%和11.6%。两组在年龄、婚姻状况、体重指数、硬膜外麻醉使用情况、引产频率、会阴切开术及肩难产方面相似。OA组旋转产钳使用频率更高（16.2%对5.9%，P = 0.03），出生体重更大（3304±526 g对3092±777 g，P = 0.004），白人女性比例更高（48.8%对34.3%，P = 0.04）。总体而言，35%的产钳分娩导致三度或四度裂伤。与OA组相比，OP组肛门括约肌损伤发生率显著更高（51.5%对32.9%，P = 0.003），优势比为2.2（95%置信区间：1.3 - 3.6）。在控制了枕后位、产妇体重指数、种族、第二产程时长、会阴切开术、出生体重及旋转产钳等因素的逻辑回归模型中，枕后位胎儿头部位置与肛门括约肌损伤相关的可能性是枕前位的3.1倍（95%置信区间：1.6 - 6.2）。
产钳辅助阴道分娩与肛门括约肌损伤风险增加有关。在这群产钳分娩病例中，与枕前位相比，枕后位会进一步增加三度或四度裂伤的风险。
