MONTREAL — Vaginal delivery is associated with a near twofold increased odds of pelvic floor disorders, compared with cesarean delivery and nulliparity, according to results of a large epidemiologic study.
“This study finally gives us some numbers to hang our hat on, with respect to pelvic floor dysfunction, when we are counseling patients about vaginal versus cesarean delivery,” the study's principal investigator, Emily Lukacz, M.D., said at the annual meeting of the International Continence Society.
“A twofold increased odds of a pelvic floor disorder sounds like a lot, but surgical delivery is not without its own risks,” she said in an interview, adding that the protective effects of cesarean section must be balanced against the known risks of surgical delivery.
She cautioned that although the study shows an association between vaginal delivery and pelvic floor disorders, it does not prove causality.
“We are really still in the infancy of understanding the role of mode of delivery on the development of pelvic floor disorders until we can have a randomized, controlled trial of vaginal versus cesarean delivery, which will likely never happen,” said Dr. Lukacz of the University of California, San Diego Medical Center.
Still, she said that she suspects it's hard not to link the trauma caused by vaginal delivery to many of these disorders. “There are not many things that can cause that kind of damage,” she said. “However, not all women who deliver vaginally develop pelvic floor disorders. Therefore, future research should be aimed at identifying women at risk for developing pelvic floor disorders due to vaginal delivery.”
The Kaiser Permanente continence-associated risk epidemiology study was a population-based study of 12,200 randomly selected women between the ages of 25 and 84.
Using the validated Epidemiology of Prolapse and Incontinence Questionnaire, researchers assessed participants for symptoms and signs of stress urinary incontinence, overactive bladder (with or without leakage), and anal incontinence (leakage of solid, liquid, or gas), as well as pelvic organ prolapse.
A total of 4,103 surveys had sufficient information for analysis, and these were then categorized into three birth groups. The nulliparous group (19%) included women who had never been pregnant, or who had never delivered a baby larger than 4.5 pounds. The cesarean section group (10%) included women who had delivered only by cesarean section (with or without prior labor), or with no vaginal deliveries of more than 4.5 pounds. The vaginal delivery group (71%) included women with a history of a vaginal delivery of more than 4.5 pounds.
After adjusting for age, BMI, and parity, the vaginal delivery group had higher rates of every disorder, compared with the nulliparous and cesarean groups. (See chart.)
The study results are “highly controversial” but in line with other research, particularly the large Norwegian Epidemiology of Incontinence in the County of Nord-Trøndelag (EPINCONT) study. That Norwegian study found vaginal delivery associated with a higher risk (odds ratio 2.2) of moderate to severe urinary incontinence compared with cesarean delivery (N. Engl. J. Med. 2003;348:900–7), Dr. Lukacz said.
Dr. Lukacz and her team also performed a subanalysis of the cesarean section group to assess the impact of cesarean sections that involved labor and those that did not; they found a significantly higher prevalence of prolapse in the group that underwent labor, as well as a trend toward a higher prevalence of stress incontinence.
The rates of overactive bladder, anal incontinence, and overall pelvic floor disorders did not differ significantly between groups in the subanalysis. “The mechanism of trauma may be different for the development of the different disorders,” she suggested.
Dr. Lukacz noted that while great efforts continue in the treatment of incontinence, a shift in focus toward prevention is crucial. “The key is being able to identify who is at risk for developing those conditions—and this is a step in that direction.”
The study was funded by the National Institute of Child Health and Human Development.