Evidence of pelvic floor nerve injury after routine vaginal birth

Aug 20 2004

Researchers at Oregon Health & Science University have discovered evidence of pelvic floor nerve injury after routine vaginal birth. Their findings are reported in this month's issue of Obstetrics and Gynecology, the official publication of the American College of Obstetrics and Gynecology.

"I am studying pelvic floor nerve injury immediately after childbirth with the aim of being able to prevent pelvic floor disorders in the future. Women with pelvic floor disorders suffer from urinary and fecal incontinence as well as prolapse of the bowel, bladder and reproductive organs. (Bowel prolapse occurs when the bowel slips out of place, and pushes up against the walls of the vagina, which may cause a great deal of discomfort.) These conditions tend to occur in midlife or in older women, but they also are linked to childbirth occurring 20 to 30 years earlier. Being able to diagnose an injury immediately after birth will greatly increase our understanding," said W. Thomas Gregory, M.D., principal investigator and assistant professor of obstetrics and gynecology (urogynecology and reconstructive pelvic surgery), OHSU School of Medicine. Gregory also is a member of the OHSU Center for Women's Health.

"The injuries seen in this group of women were very mild and none of the women had any symptoms of pelvic floor disorders. We know from previous studies that profound nerve injury is associated with immediate urinary or fecal incontinence. We also know that the pelvic nerves can heal and regenerate after birth. Whether or not the regenerated nerves will function well later in life is not known," Gregory said.

For the short term, this adds to the growing controversy regarding maternal choice of Caesarean birth. Women may choose a Caesarean section to prevent pelvic floor damage. The researchers for this study do not believe that these findings are a basis for recommending routine Caesarean section. Although there is mounting evidence that pelvic floor disorders are highly associated with vaginal childbirth, more data is needed regarding the increased, occasionally severe, complications associated with Caesarean deliveries, especially the complications that can occur in subsequent pregnancies, Gregory said.

"In our previous work, we found that women have a one in nine lifetime risk of undergoing surgery for urinary incontinence and/or pelvic organ prolapse -- thus most women seem to recover despite sustaining nerve injury. Gregory's work gives us a tool to measure what happens at birth that may lead to pelvic floor injury. It is our goal to use this information to guide changes in obstetric practice to prevent pelvic floor injury during birth," said Amanda Clark, M.D., co-investigator of the study. Clark is the division chief of research, urogynecology and reconstructive pelvic surgery, and associate professor of obstetrics and gynecology, OHSU School of Medicine and a member of the Center for Women's Health.

"We don't know who is at risk for pelvic floor nerve injury, and we are not advocating Caesarean deliveries for everyone. We recommend that pregnant women discuss this issue carefully with their obstetrician or certified nurse-midwife," Gregory said.

Urogynecology and reconstructive pelvic surgery is a new subspecialty of obstetrics and gynecology that provides care for women with pelvic floor disorders. The OHSU urogynecologists perform basic and clinical research and are investigating whether injury to the muscles, nerves or intervening tissue occurs with descent of the baby's head during delivery. The researchers studied two groups of women. The first group comprised 28 women who had never had a child and who did not have pelvic nerve injury. The second group of 23 women was 12 weeks postpartum with their first child. Using tests similar to those used to diagnose nerve and muscle diseases such as Lou Gehrig's disease, and carpal tunnel syndrome, they showed that after uncomplicated vaginal deliveries, women had abnormalities consistent with mild nerve injury when compared with a group of women who had never given birth. Other researchers in the study are Jau-Shin Lou, M.D., Ph.D., associate professor of neurology and Amy Stuyvesant, research assistant, OHSU School of Medicine.