Incontinence twice as likely with vaginal birth.(Gynecology)

RANCHO MIRAGE, CALIF. -- Women who had delivered vaginally were more than twice as likely to report stress urinary incontinence as were women who had delivered only by cesarean section in a study of 271 sets of identical twin sisters.

In a longstanding debate about the relationship of obstetric delivery mode and subsequent urinary incontinence, difficulty separating genetic from environmental factors has confounded study results. This study is the first on the subject with good control over the genetic factors, Roger P. Goldberg, M.D., said at the annual meeting of the Society of Gynecologic Surgeons.

Surveys completed by 542 women at the world's largest annual gathering of twins in 2003 and 2004 showed that 52% reported stress urinary incontinence.

Twelve percent of the women had more than five episodes of stress urinary incontinence per week.

Among all pairs of sisters, nulliparous women were the least likely to have stress incontinence, and having more than two births conferred nearly a fivefold increased risk of incontinence, compared with nulliparous women. With increasing numbers of vaginal births, the incontinence rate rose as high as 66%, said Dr. Goldberg of Northwestern University, Chicago, and his associates.

Higher body mass index (BMI) also was a risk factor for incontinence.

A second regression analysis of 196 sisters who were parous found that delivery mode was the major factor determining the risk of stress urinary incontinence, with vaginal birth doubling the chance of incontinence. "Parity and BMI were washed out by the effect of birth mode," he said.