Obstetric events leading to anal sphincter damage

Department of Obstetrics and Gynaecology, University College Dublin, National Maternity Hospital, Ireland.
Obstetrics and Gynecology (Impact Factor: 4.37). 01/1999; 92(6):955-61. DOI: 10.1016/S0029-7844(98)00255-5
Source: PubMed

ABSTRACT To identify the obstetric factors relating to anal sphincter injury at first vaginal delivery by prospective cohort study of primiparous women.
We compared the results of a bowel function questionnaire and anal vector manometry before and 6 weeks after delivery in 184 primiparous women. Postpartum, pudendal nerve conduction latency was measured in all women, and anal endosonography was performed in 81 with altered fecal continence or abnormal physiology.
Sixteen (9%) women, none of whom had altered fecal continence, were delivered by cesarean. After vaginal delivery, 42 of 168 (25%) women had impairment of fecal continence and 76 of 168 (45%) women had abnormal anal physiology. Instrumental vaginal delivery was associated with an 8.1-fold (95% confidence interval [CI] 2.7, 24.0; P < .001) risk of anal sphincter injury and a 7.2-fold (95% CI 2.8, 18.6; P < .001) risk of symptoms. Duration of the second stage of labor beyond 60 minutes led to a 1.7-fold (95% CI 1.14, 2.48; P;< .01) risk of anal sphincter injury and a 1.6-fold (95% CI 1.03, 2.6, P = .01) risk of symptoms. Epidural analgesia, used in 58% of vaginal deliveries, prolonged the second stage of labor (P = .004; odds ratio [OR] 7.7; 95% CI 4.0, 14.7) and was associated with increased risk of sphincter injury (P = .02; OR 2.1; 95% CI 1.1, 4.0) and of symptoms (P = .02; OR 2.0; 95% CI 1.1, 3.7).
Instrumental delivery and a second stage of labor prolonged by epidural analgesia are the obstetric factors that pose the greatest risk of injury to the anal sphincter mechanism in primiparous vaginal delivery.

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    ABSTRACT: Functional asymmetry of pelvic floor innervation has been shown to exist in healthy subjects, and has been proposed to be a predictor of increased risk for fecal incontinence in case of trauma. However, this remains to be shown for different clinical conditions such as traumatic childbirth. A conventional surface EMG system was used to assess the innervation of the external anal sphincter. A symmetry index was used to define the relative EMG amplitude asymmetry of the external anal sphincter between 0 (symmetric) and 1 (asymmetric). Three cohorts were studied: 40 nulliparous women in the third trimester (Study 1), 15 primiparous women within 6 months following vaginal delivery without clinically apparent anal sphincter trauma (Study 2), and 50 women after childbirth-related third or fourth degree perineal tear 6-12 months postpartum (Study 3). Furthermore, all women underwent conventional anorectal manometry. Sixteen or forty nulliparous women reported signs of fecal incontinence; however, relative asymmetry was not correlated to symptom severity (P = 0.345), and not to manometric measures (Study 1). In Study 2, Women who had suffered clinically apparent anal sphincter trauma (P = 0.07) tended to have a stronger association between incontinence and asymmetry. In Study 3, 19/50 women reported moderate to severe incontinence. Asymmetry and symptom severity were significantly correlated (P < 0.001). Patients with incontinence had a significantly higher asymmetry score than their continent counterparts. Functional asymmetry of anal sphincter innervation is significantly associated with incontinence symptoms, but only after childbirth-related sphincter injuries and therefore, should be regarded as an additional risk factor.
    Neurourology and Urodynamics 01/2007; 26(1):134-9. DOI:10.1002/nau.20307 · 2.46 Impact Factor
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    ABSTRACT: Methods This was a prospective case controlled study. 52 pregnant women whose first baby was delivered by forceps were studied antenatally during their second pregnancy. A control group consisted of 20 women whose first baby was delivered by spontaneous vaginal delivery. Patients were assessed antenatally using a bowel function questionnaire derived from Jorge and Wexner (4) , end oanal ultrasound and anal manometry. These tests were repeated at 12 weeks postpartum. The anal sphincter was visualised using a Bruel and Kjaer 10MHz endoanal ultrasound probe. A consultant radiologist blind to the patient's history reported all scans. Anorectal manometry was performed using a Synectics PC Polygraf System to record mean maximum resting and squeeze anal sphincter pressures. Results Antenatally, the median continence score in the forceps group was 0 (mean 0.98, range 0-5). At manometry the median resting pressure was 43mmHg and median squeeze pressure was 71mmHg. 71% of patients had some external anal sphincter defect noted on endoanal ultrasound. The median continence score in the control group was 0 (range0 -3) and they had a median resting pressure of 60mmHg (p=0.014) and median squeeze pressure of 114mmHg (p=0.004). These pressures did not deteriorate significantly following second vaginal delivery. Following subsequent vaginal delivery in the forceps group, 46 patients had a median continence score of 0 (p=0.745). The median squeeze pressure was 74mmHg (p=0.9778) and median resting pressure was 46mmHg (p= 0.4071). There was no significant difference in endoanal ultrasound findings postnatally in either the forceps or the control group. Conclusions There is a high incidence of occult/asympt omatic anal sphincter injury in women following forceps delivery. Anal manometry pressures were significantly lower in women delivered by forceps with greater evidence of sphincter defect on endoa nal ultrasound compared to a control group following spontaneous vaginal delivery. Our results indicate that subsequent vaginal delivery did not lead to a significant deterioration in anal sphincter function in either group.
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