Among the 206 women without detected sphincter tears at their first vaginal delivery, 52 (25%) reported some degree of anal incontinence at 9 months. At the 5-year follow-up, 66 women (32%) reported symptoms of anal incontinence (P < .001) (Figure 1). Twenty-seven percent of the women were incontinent to flatus only whereas 5% also experienced fecal incontinence (Table 3).
Nine of the 36 women with a sphincter tear at the first delivery (25%) had no additional childbirths during the study period. Of these 9 women, 4 (44%) reported anal incontinence symptoms at 9 months postpartum, and this prevalence was identical (44%) at the 5-year follow-up (P = .09) (Fig. 2). Twenty-seven of the 36 women (75%) with a sphincter tear at the first delivery had 1 or more subsequent childbirths. Of these 27 women, 12 (44%) reported anal incontinence symptoms at the 9-month follow-up and 15 (56%) at the 5-year follow-up (P = .009).
Forty-four of the 206 women without a sphincter tear at the first delivery (21%) had no additional childbirths during the study period. Of these 44 women, 9 (20%) reported symptoms of anal incontinence at the 9-month follow-up and 11 (25%) at the 5-year follow-up (P < .001). One hundred sixty-two of the 206 women without a sphincter tear at their first delivery (79%) had 1 or more subsequent childbirths during the study period. Of these 162 women, 44 (27%) reported anal incontinence symptoms at 9 months postpartum and 70 (34%) at the 5-year follow-up (P < .001).
Multivariable logistic regression analysis was used to analyze obstetric risk factors potentially involved in the development of anal incontinence 5 years postpartum. Age, sphincter tear at the first delivery, and subsequent childbirth were independent risk factors. Analyzed variables and odds ratios (ORs) are shown in Table 4. The presence of anal incontinence after the first delivery was the strongest risk factor according to multivariable regression, and this factor could be used as a predictor of persistent anal incontinence at 5-year follow-up. For women without symptoms of anal incontinence before their first pregnancy, anal incontinence at both 5 months (OR 3.8; 95% CI 2.0–7.3) and 9 months (OR 4.3; 95% CI 2.2–8.2) postpartum was a significant risk factor for persistent symptoms at 5-year follow-up. When analyzing women with sphincter tears separately, corresponding ORs were 5.3 (95% CI 1.2–23.3) at 5 months and 7.8 (95% CI 1.6–38.8) at 9 months.
We chose to study primiparous women in this follow-up study so that we could assess the long-term impact of vaginal childbirth on anal incontinence. Primiparous women have a low frequency of anal incontinence symptoms, but they have an increased risk of anal sphincter tears compared with multiparous women.11
In the present study, 15% of the primiparous women experienced a sphincter tear at their first delivery. Forty-four percent of the women with sphincter tears had symptoms of anal incontinence at 9-month follow-up, and the frequency of symptoms remained high at the 5-year follow-up (53%). Our results are comparable with previous studies,1,2,6 where a prevalence of up to 50% has been reported. Reasons for these poor results may include inadequate surgical technique or insufficient healing of the primary repair. In a study by Sultan et al,1 a morphologic sphincter defect persisted in up to 85% of primary repaired sphincter injuries when assessed with endoanal ultrasonography at follow-up.
Anal incontinence in women without clinically diagnosed sphincter tear may be due to neurologic impairment or occult sphincter injuries. Sultan et al12 reported a strong association between occult injuries and anal incontinence, and these findings are supported by Zetterstrom et al.13
Among women without a clinically diagnosed sphincter tear, 25% reported anal incontinence at 9 months postpartum. Most of these symptoms were mild, and the majority had only infrequent symptoms of flatus (Table 4). After 5 years the reported prevalence was 32%, which is a significant increase (P < .001). Studies with long-term follow-up data of anal incontinence after uncomplicated deliveries are few, but Ryhammer et al14 found a 5% incontinence rate among women who delivered 2 to 13 years earlier. Many of these women also had subsequent deliveries. The higher prevalence of anal incontinence in our study might be explained by our decision to define involuntary gas leakage less than once a week as incontinence. Although this symptom could be considered mild and of no importance, to some women it can mean a great deal of embarrassment and psychological suffering. However, the present study was not designed to study quality-of-life aspects in relation to the frequency or severity of anal incontinence.
The impact of subsequent deliveries on anal incontinence is controversial. Fynes et al15 found that primiparous women with persistent anal incontinence deteriorated after a second vaginal delivery. In a Danish study, Ryhammer et al14 reported a significant increase in incontinence symptoms after the third delivery in women without clinical sphincter injury, whereas Hojberg et al16 could not find this association. The present study showed a significant increase in anal incontinence among women with additional deliveries. Most published data support our finding that additional deliveries may increase the risk for anal incontinence.
Our study demonstrated a long-term increase in incontinence symptoms after additional childbirths in women with previous sphincter tears. This finding is supported by several previous studies. In the study by Fynes et al,15 primiparous women with transient symptoms or occult sphincter injury were at increased risk for developing anal incontinence after a second delivery. In a more recent study, Faltin et al17 found an increased prevalence of anal incontinence after previous sphincter tear and subsequent delivery, and Payne et al18 reported an increased risk for a recurrent sphincter injury at subsequent vaginal deliveries.
In the present study, the incontinence rate in the group without additional deliveries and no sphincter injuries was 25% after 5 years, compared with 34% in the group with 1 or more subsequent deliveries. In the study by Faltin et al,17 incontinence symptoms increased from 3% to 10% after a second delivery among women who had intact sphincters (according to endoanal ultrasonography) after their first delivery. In our study, even mild and sporadic (< 1 per week) symptoms of gas incontinence were reported, which may explain the higher prevalence.
The present study indicates that increasing maternal age is a risk factor for developing anal incontinence. Our results indicate that a 30-year-old woman has twice as high a risk of developing anal incontinence compared with a 20-year-old woman. This finding is consistent with previously reported findings,5and is of importance because maternal age at the time of first childbirth continues to increase.19
Postpartum anal incontinence was an important predictor of persistent symptoms, particularly among women with a previous sphincter tear. These women had an almost 8 times increased risk for symptoms at 5 years if they reported symptoms at 9 months postpartum. Adding this finding to the increased risk of incontinence after subsequent delivery, we can make a firm argument against exposing the anal sphincter mechanism to the risk of functional impairment by a further vaginal delivery.
Our results suggest that patients with anal incontinence symptoms 9 months postpartum usually do not improve with time. In fact, the majority of these patients deteriorated with time, particularly if they underwent additional deliveries. Several previous reports have concluded that sphincter tear at delivery is the major cause of anal incontinence and that not all of these injuries are recognized at the time of delivery.12,20 Far from all women with anal incontinence at 9 months in the present study had a clinical detected sphincter injury, and it is plausible that some of these symptoms were the consequence of an occult injury. Although the present study did not collect information regarding occult injuries, a higher awareness of such injuries, resulting in meliorating clinical examinations of women after delivery, could have affected the outcome. Adding an endoanal ultrasound examination to the clinical examination immediately after parturition may also be of value. However, further studies on this matter are needed.
Unfortunately, the results of sphincter repair after delivery can be unsatisfying,1,2,21 and studies evaluating new treatment strategies are needed. At our institution, we have developed collaboration between the gynecologic and surgical departments to optimize surgical treatment of primary obstetric sphincter injuries. We are currently studying whether delayed primary suture of sphincter tears or other treatment factors can improve continence after sphincter repair.
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© 2004 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.
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