Pelvic Floor Disorder Risk Highest With Assisted Vaginal Delivery

Nancy A. Melville

December 18, 2018

The risk of pelvic floor disorders after childbirth, ranging from urinary incontinence to pelvic organ prolapse, are significantly lower with cesarean delivery compared with spontaneous vaginal delivery, and operative vaginal delivery, such as the use of forceps, has the highest risk of the disorders, according to a study of more than 1500 women followed up to almost two decades after childbirth.

"Results of this study showed a substantial difference in pelvic floor disorder incidence based on a woman's obstetrical characteristics," say Joan L. Blomquist, MD, of the Department of Gynecology, Greater Baltimore Medical Center, Maryland, and colleagues, in their article published online December 18 in JAMA.

"The cumulative incidence of each pelvic floor disorder was significantly associated with delivery mode," they add.

Studies have shown as many as 25% of women in the United States have at least one pelvic floor disorder, and the rate is more than twice as high for women over 80 years. Although childbirth is a known key risk factor, research is lacking on long-term risks and the association with specific obstetrical procedures.

"Data from the present study build on those observations by providing a more complete picture of incidence over time," Blomquist and colleagues note.

However, in an interview with Medscape Medical News, Blomquist would not be drawn on how this research should inform individual choices about birth delivery methods.

She noted that a multitude of considerations go into decisions about birth delivery mode, and this study is not designed to suggest recommendations for any one over another.

"This is just one piece in the very large puzzle that a provider and patient need to consider when determining the best delivery mode for that patient," she said.

"The study does not give information about who is the best candidate for which delivery type. However, it does tell us that if someone had an operative vaginal delivery, they are at higher risk of developing these disorders in the future."

"As a result, there may be a role for secondary prevention, such as avoidance of obesity or certain exercises, in these high-risk populations."

Women Followed-Up for 18 Years After Giving Birth

For the analysis, Blomquist and colleagues evaluated data on 1528 women in the longitudinal Mother's Outcome After Delivery (MOAD) study from October 2008 to December 2013.

The women, who were enrolled 5 to 10 years after their first delivery, were followed-up annually for up to 9 years. The longest time after first delivery when a participant was seen in the study was 18.7 years.

Participants were a median age of 30.6 years at first delivery and had 778 cesarean births, 565 spontaneous vaginal births, and 185 operative vaginal births, including vacuum assistance (ventouse) or use of forceps.

Most (72%) were multiparous at enrollment, and among those women the median age at enrollment was 38.3 years. Outcomes were assessed annually using the Epidemiology of Prolapse and Incontinence Questionnaire (EPIQ) and a physical examination (gynecologic, height, and weight).

Over a median follow-up of 5.1 years, there were 138 cases of stress urinary incontinence, 117 cases of overactive bladder, 168 cases of anal incontinence, and 153 cases of pelvic organ prolapse.

For those in the reference group of spontaneous vaginal delivery, the 15-year incidence of pelvic floor disorders following the first childbirth was 34.3% for stress urinary incontinence, 21.8% for overactive bladder, 30.6% for anal incontinence, and 30.0% for pelvic organ prolapse.

Comparatively, those in the cesarean delivery group had a significantly lower incidence of stress urinary incontinence (adjusted hazard ratio [aHR], 0.46) and overactive bladder (aHR, 0.51), and a much lower risk of pelvic organ prolapse (aHR, 0.28).

Women who had operative vaginal delivery meanwhile had a significantly higher hazard of anal incontinence (aHR 1.75) and pelvic organ prolapse (aHR 1.88), compared with the reference group of spontaneous vaginal delivery.

Genital Hiatus Size Also Plays a Role

The researchers also found that genital hiatus size, the distance between the external urethral meatus and posterior midline hymen, was associated with risk of pelvic organ prolapse. An enlarged genital hiatus is also referred to by some providers as a "relaxed vaginal outlet."

Among women with the same mode of delivery, including women in the cesarean birth group, there was a statistically and clinically significant association between genital hiatus size and pelvic floor disorder.

Compared with a size of 2.5 cm or less, the adjusted hazard ratio of pelvic organ prolapse was significantly higher with genital hiatus size of 3 cm (aHR, 3.0) and even greater with a size of 3.5 cm or higher (aHR, 9.0).

These findings suggest genital hiatus could be a useful predictor. "Genital hiatus size is viable as a marker to monitor the risk of pelvic organ prolapse over time," the authors suggest.

"Indeed, the changes in genital hiatus may actually be a mechanism for the development of pelvic organ prolapse, regardless of delivery mode," they suggest.

Pelvic Floor Disorders Develop at Different Times, Have Different Causes

The longitudinal nature of the study adds to prior research by showing the incidence of pelvic floor disorders in relation to the duration of time since childbirth, Blomquist explained to Medscape Medical News.

"This study allows us to see patterns of incidence of the various pelvic floor disorders over the first two decades after childbirth," she said.

"In addition to finding that the delivery mode is associated with the incidence of pelvic floor disorders, we also noted different [latency] patterns between the different pelvic floor disorders."

For example, the findings indicate that the peak incidence of stress incontinence is within the first 5 years after childbirth, whereas pelvic organ prolapse has a longer latency, with the peak incidence more than 20 years after childbirth, Blomquist explained.  

This indicates that there are likely different causes of the various pelvic floor disorders, she and her colleagues conclude.

The study received support from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Blomquist has reported no relevant financial relationships.

JAMA. Published December 18, 2018. Abstract

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