Elsevier

Obstetrics & Gynecology

Volume 98, Issue 2, August 2001, Pages 225-230
Obstetrics & Gynecology

Original research
Obstetric anal sphincter lacerations

https://doi.org/10.1016/S0029-7844(01)01445-4Get rights and content

Abstract

OBJECTIVE:

To estimate the frequency of obstetric anal sphincter laceration and to identify characteristics associated with this complication, including modifiable risk factors.

METHODS:

A population-based, retrospective study of over 2 million vaginal deliveries at California hospitals was performed, using information from birth certificates and discharge summaries for 1992 through 1997. We excluded preterm births, stillbirths, breech deliveries, and multiple gestations. The main outcome measure was obstetric anal sphincter laceration (third and fourth degree).

RESULTS:

The frequency of anal sphincter lacerations was 5.85% (95% confidence interval [CI] 5.82, 5.88), decreasing significantly from 6.35% (95% CI 6.27, 6.43) in 1992 to 5.43% (95% CI 5.35, 5.51) in 1997 (P < .01). Using logistic regression analysis, we identified primiparity as the dominant risk factor (odds ratio [OR] for women with prior vaginal birth 0.15; 95% CI 0.14, 0.15). Birth weight over 4000 g was also highly significant (OR 2.17; 95% CI 2.07, 2.27). Lacerations occurred more often among women of certain racial and ethnic groups: Indian women (OR 2.5; 95% CI 2.23, 2.79) and Filipina women (OR 1.63; 95% CI 1.50, 1.77) were at highest risk. Episiotomy decreased the likelihood of third-degree lacerations (OR 0.81; 95% CI 0.78, 0.85), but increased the risk of fourth-degree lacerations (OR 1.12; 95% CI 1.05, 1.19). Operative delivery increased the risk of sphincter laceration, with vacuum delivery (OR 2.30; 95% CI 2.21, 2.40) presenting a greater risk than forceps delivery (OR 1.45; 95% CI 1.37, 1.52).

CONCLUSION:

Anal sphincter lacerations are strongly associated with primiparity, macrosomia, and operative vaginal delivery. Of the modifiable risk factors, operative vaginal delivery remains the dominant independent variable.

Section snippets

Materials and methods

We employed a database of the California Office of State Health Planning and Development, which links California birth certificates to maternal and newborn discharge records since 1992. Ninety-eight percent of all California deliveries are included in the database. Discharge data include diagnostic codes (International Classification of Diseases, 9th Revision) and procedural codes (Current Procedural Terminology). This study was approved by the institutional review boards of the California

Results

The study population included 2,101,843 births. The overall frequency of third- and fourth-degree laceration was 5.85% (123,009 of 2,101,843) (95% CI 5.82, 5.88). The incidence of anal sphincter lacerations decreased significantly over the 6 years of data collection, from 6.35% (95% CI 6.27, 6.43) in 1992 to 5.43% (95% CI 5.35, 5.51) in 1997 (P < .01) (Cochran-Armitage trend test for binomial proportions χ2: 19.38; P < .001; Figure 1).

Table 1 characterizes the study population and summarizes

Discussion

The strength of this study is the size and heterogeneity of the population examined. Prior studies5, 6, 7, 8 have included a relatively small number of cases (276 to 1124 sphincter lacerations), usually from a single institution. The large number of cases in this report (123,009 sphincter lacerations) allows us to simultaneously examine a large number of risk factors. Prior studies found anal sphincter lacerations in 2.2% to 19% of deliveries.5, 6, 7, 8 In our population, 5.85% (95% CI 5.82,

References (18)

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