Dec. 2, 2005 - Doctors think it's true. Patients think it's true. And urogynecologist Gunhilde M. Buchsbaum, MD, thought vaginal childbirth put women at risk of urinary incontinence.
And she has a good reason to think so. Buchsbaum's team studied pairs of postmenopausal sisters. In each pair, one sister had at least one child by vaginal delivery. The other never had a child. No matter how the researchers looked at it, the results came out the same.
"In a group of sisters where half were childless and half had children, we found no difference in urinary incontinence," Buchsbaum tells WebMD. "There was no difference in type of incontinence, overall prevalence of incontinence, or severity of incontinence."
The findings appear in the December issue of Obstetrics & Gynecology.
Sisters and Urinary Incontinence
It's very common for doctors to think that vaginal delivery puts a woman at risk of urinary incontinence. In fact, a recent survey found that 62% of urogynecologists would support a woman's decision to choose to have a C-section to prevent it.
Yet studies on childbirth and urinary incontinence are divided. Some show a risk, others fail to find one.
Buchsbaum's interest in the issue came when she was contacted by a nearby convent.
"The mother superior said, 'I think we have a problem,'" she recalls.
As they reached the age of menopause, many of the nuns were suffering urinary incontinence. Yet medical examination revealed the obvious: None of the women had ever had a child.
Preliminary studies led Buchsbaum to suspect that childbirth is not a woman's major lifetime risk factor for urinary incontinence. So she and her colleagues designed the current study.
Sisters' Sisters and Urinary Incontinence
At first, the researchers looked at the convent sisters and the sisters' married sisters. The study was later expanded to include other postmenopausal sister pairs where one had had a child by vaginal delivery and the other never gave birth.
The researchers looked at whether the women suffered urinary incontinence. They looked at whether they suffered stress incontinence (involuntary urination caused by activity such as coughing), urge incontinence (urination caused by overactive bladder), or mixed incontinence. They looked at incontinence severity. In every regard, the women who gave birth were no more likely to suffer urinary incontinence than their childless sisters.
"Everyone says vaginal delivery causes incontinence, so we looked at sisters sharing a genetic pool, to see what is the greatest risk factor -- having kids or coming from same family," Buchsbaum says. "Childbirth is no risk factor -- none."
Genetic Risk for Urinary Incontinence?
While having a child wasn't a risk for urinary incontinence, having a sister with the problem was a different story.
"Out of every three sister pairs, two had same status: Either both leaked urine or neither leaked urine," Buchsbaum says. "That's more than you would see by chance."
And when one sister had urinary incontinence and the other didn't, the sister with the problem was no more likely to have given birth than to be childless.
"So we think there is probably some genetic component that may predispose somebody for incontinence or not," Buchsbaum says. "Because we saw women with eight kids and no incontinence."
This doesn't surprise Niall Galloway, MD, medical director of the Emory Continence Center at the Emory University School of Medicine in Atlanta.
"I believe, based on the medical literature and our own experience, that urinary incontinence is a familial disease," Galloway tells WebMD. "The risks are going to be greater to daughters of women who already have these problems."
Not all women are built the same way, Galloway notes. This means vaginal delivery has different consequences for different women.
"The pelvic floor of one woman is different from another's, just as the telephone book of Ellijay, Ga., is different from that of Atlanta," Galloway says. "Life is not fair. Some women are going to be able to produce multiple children by vaginal delivery and never have a moment's setback. Others are going to have a single child, and their pelvic floor will be damaged forever."
Childbirth Still a Suspect in Earlier-Life Incontinence
Buchsbaum's study finds no lifetime risk of urinary incontinence. She is quick to point out that it does not say anything about whether vaginal delivery brings on urinary incontinence sooner than it might otherwise appear.
The Buchsbaum study is important, says Neeraj Kohli, MD, MBA, director of urogynecology at Brigham and Women's Hospital and assistant professor at Harvard Medical School, Boston. But Kohli says that vaginal childbirth does appear linked to earlier onset of urinary incontinence.
"I see patients who are 40, who had their last delivery five years ago, and they have urinary incontinence and their sisters don't have it," Kohli tells WebMD. "As patients get older, vaginal delivery is less of a causative issue. But in the younger population, vaginal deliver might be more of a cause of pelvic-floor dysfunction -- including urinary incontinence."
Kohli agrees with Galloway that different women have different problems with vaginal delivery. And Kohli, Galloway, and Buchsbaum all agree that pregnant women considering having a C-section in order to avoid urinary incontinence should have a long talk with their doctor.
"I make recommendations specific to individual patients," Kohli says. "If someone had incontinence or pelvic prolapse after her first delivery, I might recommend C-section for her next one, because every subsequent delivery causes further trauma. If I have a small woman with a big baby, we would probably recommend C-section also. But at the end of the day, if a patient says to her doctor, 'I want a primary elective C-section,' there should be an extended discussion."
Galloway offers advice for how women can know whether their pelvic floor is well suited to withstand the rigors of vaginal delivery.
"The nerves and muscles that enervate the feet are adjacent to those responsible for the pelvic floor," Galloway says. "If you were trying to distinguish whether you are at risk or not, look and see how complete is the form and function of your feet and toes. Those with the best, most versatile feet -- who can spread their toes like fingers -- are more likely to have better function in the pelvic floor."