Discussion
Main Findings : In this randomized trial of women with
asymptomatic anal sphincter lesions resulting from a first delivery,
planned cesarean section for the second delivery was not protective
against anal incontinence at 6 months post-partum. In addition, we
failed to show any benefit of cesarean section in this population on
quantitative evaluations of urinary incontinence, sexual functions or
quality of life. These results should be useful for clinicians and
women, avoiding numerous unnecessary cesarean
sections12.
Results vis-à-vis other studies : Our findings are consistent
with those from recent observational studies, including longer follow-up16,23. In a recent observational cohort study, CS for
women with anal sphincter disruption at the first delivery was
associated with no benefit on anal incontinence 5 years after the second
delivery 16. However, most women who sustained
obstetric injuries develop anal incontinence later, after their 50s.
Nygaard et al 24 found that anal sphincter disruption
following an index delivery was a risk factor for flatus incontinence 30
years later. Some large population-based cohort studies failed to show
any difference in the incidence of flatus incontinence in women above 50
years old, according to whether they delivered vaginally or by CS17, but a recent population-based study from Sweden
found that the risk of anal incontinence was lower after CS than after
VD 25 . In this study, AI also was higher among
women who delivered by CS compared with nulliparous and higher among
nulliparous compared with men. In another study, an association has been
found between ultrasound diagnosis of anal sphincter lesions and
long-term fecal incontinence after a first delivery26. Because anal incontinence is multifactorial,
including neurological and gastro-intestinal as well as mechanical
causes, this symptom can occur without sphincter lesions and vice versa.
Anal sphincter lesions are observed by ultrasound in less than half of
women with postpartum anal incontinence 8. In an
unselected primiparous population, anal sphincter disruption was
detected by ultrasound screening after delivery in 27 % of women, most
of whom had no symptoms 27. Thus, although CS can be
protective from anal sphincter lesions 8, 9,
ultrasound evidence is one of many factors associated with anal
continence. Besides, it has been shown that the severity of the anal
sphincter lesion is an important risk factor for subsequent anal
incontinence, particularly the depth of the disruption of both the
external and internal sphincter 28. In our trial, we
did not observe a protective effect of CS in the subgroup with severe
anal sphincter ruptures (defined as >90°)(data not shown).
In another study, only 4th-degree tears were associated with an
increased risk of anal incontinence at 10 months postpartum29, but this was an exclusion criterion in our trial.
One important difference between our study and most retrospective
studies was the inclusion of women whose first delivery was by forceps,
even in the absence of a diagnosis of a third-degree perineal
laceration.
Some observational studies have shown that a subsequent vaginal delivery
following an obstetrical anal sphincter injury may result in additional
or recurrent lesions 30, which may be apparent or
occult, however without any significant change in the continence score
according to the mode of delivery. In our trial, the incidence of
repeated clinically apparent OASIS was low, since only one woman had a
repeated 3rd degree tear.
Endosonographic aggravation of external sphincter lesions occurred
significantly more often in the VD group than the CS group. These
findings may indicate that CS avoids some occult sphincter disruptions,
but on the other hand they signify that ultrasound evidence of anal
sphincter lesions is not predictive of symptoms of anal incontinence.
Clinical implications: Our results do not support a policy of
systematic prophylactic CS in women with asymptomatic ultrasound anal
sphincter lesions resulting from a first delivery. However, we cannot
exclude a protective effect of prophylactic CS for women with
symptomatic anal sphincter lesions. In a subgroup analysis, we did find
a significant benefit of CS among women with mild clinical anal
incontinence detected before the second delivery at the proctological
visit. Since it is a post-hoc analysis, it must be interpreted with
caution. Our findings underline the importance of correct diagnosis of
anal incontinence.
Because of the taboos surrounding anal incontinence, it is difficult to
reveal without meticulous questioning. In our study, 27 women
self-reported no anal incontinence at inclusion, but had a Vaizey score
≥5 at the visit with a proctologist. Comparatively to endosonography,
clinical-based diagnosis of anal incontinence is less expensive, more
accessible and appears to be more predictive of functional outcome, as
has been previously suggested in retrospective studies16,23. Thus, our findings do not support performing
anal endosonography for women with an overt OASI or forceps
instrumentation for their first delivery in order to decide on the mode
of delivery.
Research Implications : Further studies are needed to determine
whether CS may be useful in the long term, among women with mildly
symptomatic anal lesions, and if so whether women with third- or
fourth-degree perineal tears and/or forceps at their first delivery can
benefit from a proctological examination in order to make a decision
regarding their subsequent deliveries.8
Strengths/Limitations: This trial has several strengths. To our
knowledge, it is the first randomized controlled trial addressing this
issue. Also, anal incontinence was assessed with a standardized,
validated and widely used score, the Vaizey score, and sphincter lesions
were defined by endosonography. Third, the external validity was
supported by the diversity of trial settings, including teaching
hospitals and general hospitals in diverse populations from
neighborhoods ranging from poor to affluent, with no center effect.
This trial also has limits. It was necessarily unblinded, and the main
outcomes were patient-reported, thus we cannot exclude patient reporting
bias. However, all investigators were unaware of aggregate outcomes
during the study. Also, crossovers were observed (cesareans in the
vaginal delivery group and vice versa), as expected in this pragmatic
trial comparing strategies (planned CS or planned VD). Lastly, one fifth
of the randomized women did not complete the 6 months post-partum
follow-up, which could lead to attrition bias; however their
characteristics did not differ between the two study groups, and
multiple imputations were performed for missing variables and
comparisons were based on all the patients randomized.