Link Found Between Muscle Damage During Childbirth, Condition Causing Fallen Bladder, Uterus

New research from the University of Michigan Health System establishes one of the strongest connections yet discovered between muscle damage that can occur during vaginal deliveries and pelvic organ prolapse, a condition that causes the uterus, bladder or bowel to fall down later in a woman's life. This is a very common problem and requires surgery in more than 200,000 women each year. Rates were particularly high when forceps had been used to assist the delivery.

Even so, the researchers caution against Wusing these findings as support for more elective C-sections because that would result in numerous women having an operation they do not need. Rather, they say, the study results should be used to help determine how to prevent these injuries in the first place.

The study -- appearing in the February issue of the journal Obstetrics & Gynecology -- found major defects of the levator ani, an important muscle that supports the bladder and uterus, among 55 percent of women with prolapse and just 16 percent of women who don't have prolapse.

"Our findings are an important step forward in the search to identify what causes pelvic organ prolapse and subsequent difficulties with other problems, such as incontinence," says lead author John O. L. DeLancey, M.D., the Norman F. Miller Professor of Obstetrics and Gynecology at the U-M Medical School and director of pelvic floor research.

"The next step is for researchers to look at ways of preventing and treating these injuries of the levator ani muscle in order to reduce the rate of pelvic organ prolapse later in life," he says.

Pelvic organ prolapse can mean the falling of the bladder, uterus, vagina or lower bowel. One of the most common effects of the condition is urinary incontinence -- that is, the inability to control the release of urine. Many women with prolapse experience a protrusion or bulging in the vaginal area. The condition is common; one of nine women has surgery to correct prolapse and other pelvic floor disorders in her lifetime.

The U-M researchers studied 151 women with prolapse and compared them with 135 women who do not have prolapse. Magnetic resonance imaging was used to determine the extent of damage to the levator ani muscles. The women's vaginal closure force at rest and while contracting her pelvic muscle also was measured.

Women with prolapse were found to have a much higher rate of major levator ani damage than women without prolapse (55 percent compared with 16 percent). When they asked women to contract their muscles, the muscles were 40 percent weaker in women with prolapse.

In addition, about 52 percent of the women in the study with prolapse recalled having forceps used during childbirth, nearly twice the amount (about 27 percent) of women in the study who do not have prolapse who remembered that forceps were used. Thirty-one percent of women with prolapse reported a family history of the condition, compared with 13 percent of the women without prolapse.

The researchers from the Department of Obstetrics and Gynecology have joined forces with a colleague in the U-M College of Engineering, James A. Ashton-Miller, Ph.D., who has helped to create the intricate computer simulations necessary for understanding how the levator ani muscles are damaged. The computer modeling is a vital part of this line of research, DeLancey notes.

The senior author of the paper is Ashton-Miller, Ph.D., director of the Biomechanics Research Laboratories, research professor and distinguished research scientist, Mechanical Engineering Department, U-M College of Engineering, and senior research scientist, U-M Institute of Gerontology; and Daniel M. Morgan, M.D., Dee E. Fenner, M.D., Rohna Kearney, M.D., Kenneth Guire, M.S., Janis M. Miller, R.N., A.N.P., Ph.D., Hero Hussain, M.D., Wolfgang Umek, M.D., and Yvonne Hsu, M.D. All are from the pelvic floor research group at U-M. Kearney also has an appointment with University College Hospital, London, and Umek has an appointment at Medical University, Vienna, Austria.

Funding was provided by the National Institute of Child Health & Human Development, part of the National Institutes of Health.

Reference: Obstetrics & Gynecology, "Comparison of levator ani muscle defects and function in women with and without pelvic organ prolapse," Feb 1, 2007, 109 (2).

For more information, visit these Web sites:

Understanding pelvic floor disorders, information from the University of Michigan Health System: http://www.med.umich.edu/obgyn/pelvicfloor/understanding.htm

Pelvic floor disorders, information from the NICHD: http://www.nichd.nih.gov/health/topics/Pelvic_Floor_Disorders.cfm