Background
Obstetrical anal sphincter injuries are an important complication of vaginal deliveries
that may result in short- and long-term pelvic floor morbidity and a diminished quality
of life in young, healthy women. The prevalence of obstetrical anal sphincter injuries
ranges from 0.1% to 8.7%. Over recent years, there seems to be a trend of increasing
occurrence of obstetrical anal sphincter injuries worldwide. It is unclear why the
rates are rising. Previous studies have examined the effect of different risk factors
on the prevalence of obstetrical anal sphincter injuries. The change in the incidence
of some risk factors for obstetrical anal sphincter injuries can partially explain
the overall increase in obstetrical anal sphincter injuries. There is no previous
study that explored the impact of the changes of individual risk factors over time
on the risk for obstetrical anal sphincter injuries.
Objective
The main aim of this study was to examine the temporal trends in the prevalence and
odds ratio of the major risk factors known to be associated with obstetrical anal
sphincter injuries in the period from 1988 to 2016.
Study Design
This was a retrospective cohort study that included all women who underwent vaginal
deliveries between 1988 and 2016 at a tertiary university medical center. The time
intervals were divided into 4 periods (1988–1997, 1998–2007, 2008–2016, and the total
time from 1988 to 2016) and the incidence of each risk factor was calculated for each
time period. Correlation models and regression analysis were performed to examine
the association between obstetrical anal sphincter injuries and the different risk
factors over time. Furthermore, the trends in the odds ratios of the important risk
factors over the time periods were evaluated using a multivariate regression analysis
in which the primiparous women were separated from the multiparous women.
Results
During the study period, there were 295,668 vaginal deliveries. Of these, 591 women
were diagnosed with obstetrical anal sphincter injuries (0.2%). The significant risk
factors for obstetrical anal sphincter injuries (P<.05) in the multivariable analysis were the following: primiparity, vaginal birth
after cesarean delivery, vacuum extraction, and a birthweight of >4 kg. There was
a significant (P<.05) increase in the incidence over the study period for the following risk factors:
primiparity, vaginal birth after cesarean delivery, and vacuum extraction. No change
was found in the incidence of the risk factor of a birthweight of >4 kg. In addition,
we found a strengthening of the association between vaginal birth after cesarean delivery
and macrosomia with obstetrical anal sphincter injuries, as opposed to a decline in
the relative contribution of vacuum extraction to the overall risk for obstetrical
anal sphincter injuries. Moreover, we found that obstetrical anal sphincter injuries
among primiparous women increased 7-fold over the study period but was unchanged among
multiparous women.
Conclusion
We have shown significant (P<.05) temporal trends in the incidence and odds ratio of some of the known risk factors
for obstetrical anal sphincter injuries. A better understanding of the changes in
the incidence and specific contribution of important risk factors for obstetrical
anal sphincter injuries may explain, in part, the worldwide increase in the prevalence
of this important and detrimental complication of vaginal birth.
Key words
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Article info
Publication history
Published online: October 05, 2020
Accepted:
September 26,
2020
Received:
August 22,
2020
Footnotes
The authors report no conflict of interest.
Cite this article as: Ekstein-Badichi N, Shoham-Vardi I, Weintraub AY. Temporal trends in the incidence of and associations between the risk factors for obstetrical anal sphincter injuries. Am J Obstet Gynecol MFM 2021;3:100247.
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