McLeod N L, Gilmour D T, Joseph K S, Farrell S A, Luther E R
Department of Obstetrics and Gynaecology, Dalhousie University, Halifax, Nova Scotia, Canada.
J Obstet Gynaecol Can. 2003 Jul;25(7):586-93. doi: 10.1016/s1701-2163(16)31018-0.
(1) To identify independent risk factors for anal sphincter laceration, (2) to determine the trend in rates of anal sphincter laceration over a 10-year period, and (3) to examine the impact of temporal trends in risk factors on anal sphincter laceration rates.
Population-based data were obtained from the Nova Scotia Atlee Perinatal Database, on 91 206 women who had a singleton vaginal live birth > or =500 g for the years 1988 to 1997. Risk factors for anal sphincter laceration were identified using stepwise logistic regression. A multivariate model was used to study temporal changes in laceration rates after controlling for changes in parity, episiotomy rates, operative vaginal deliveries, birth weight, prolonged second stage of labour, and other determinants.
Nulliparity (relative risk [RR] = 6.97), occiput posterior position (RR = 2.44), non-vertex presentations (RR = 2.27), second stage > or =120 min (RR range = 1.47-2.02), delivery by an obstetrician (RR = 1.30), and birth weight > or =3000 g (RR range = 1.43-6.63) increased the risk of laceration. Instrument-assisted delivery involved risks that ranged from a 2-fold increase for a vacuum-assisted delivery (RR = 2.15) to a greater than 5-fold increase for a forceps delivery after an unsuccessful vacuum extraction (RR = 5.69). Episiotomy, particularly midline incisions, increased the risk of laceration (RR = 2.57). The risk of a sphincter laceration increased 2-fold from 1988 to 1997, despite controlling for risk factors.
Sufficient evidence exists about the risk factors for anal sphincter laceration to permit modification of management of labour and delivery to minimize the risk of anal sphincter laceration. Increased awareness of the clinical importance of recognition and repair of anal sphincter laceration may explain the rising incidence.
（1）确定肛门括约肌撕裂的独立危险因素；（2）确定10年间肛门括约肌撕裂发生率的变化趋势；（3）研究危险因素的时间趋势对肛门括约肌撕裂发生率的影响。
从新斯科舍省阿特利围产期数据库获取1988年至1997年期间91206例单胎阴道活产且出生体重≥500g的妇女的基于人群的数据。使用逐步逻辑回归确定肛门括约肌撕裂的危险因素。在控制了产次、会阴切开率、阴道助产、出生体重、第二产程延长及其他决定因素的变化后，采用多变量模型研究撕裂发生率的时间变化。
初产（相对危险度[RR]=6.97）、枕后位（RR=2.44）、非头位（RR=2.27）、第二产程≥120分钟（RR范围=1.47-2.02）、由产科医生接生（RR=1.30）及出生体重≥3000g（RR范围=1.43-6.63）会增加撕裂风险。器械助产的风险范围从真空助产时增加2倍（RR=2.15）到真空吸引失败后产钳助产时增加超过5倍（RR=5.69）。会阴切开，尤其是中线切开，会增加撕裂风险（RR=2.57）。尽管控制了危险因素，但从1988年到1997年，括约肌撕裂的风险仍增加了2倍。
关于肛门括约肌撕裂的危险因素有充分证据，可据此调整分娩管理以尽量降低肛门括约肌撕裂的风险。对肛门括约肌撕裂识别和修复的临床重要性认识的提高可能解释了发病率的上升。
