Although the etiology of pelvic organ prolapse and incontinence in older women is believed to be multifactorial, trauma related to vaginal childbirth usually is implicated as a major contributing factor. Studies have identified damage to the pudendal nerve and tissues supporting the bladder neck as contributing to the development of incontinence in the future, but most studies have been retrospective or had methodologic weaknesses. Dietz and Bennett used a prospective observational study to document the effects of childbirth-related trauma on pelvic support structures in nulliparous women.

The authors recruited 200 women scheduled to deliver their first child at an Australian university hospital. The women were assessed at six to 18 weeks’ gestation and again at 32 to 37 weeks’ gestation by focused interview, paper-towel test, flowmetry, and translabial ultrasonography. The mobility of the urethra, bladder, cervix, and rectal ampulla were determined by ultrasound measurements in the supine position, after voiding, and on Valsalva maneuver. These assessments were repeated at two to five months after delivery, but the post-partum assessors were not informed of data concerning the delivery.

Only 173 women were assessed at 32 to 37 weeks’gestation. Of these, 57 percent had vaginal deliveries, 5 percent had planned or prelabor cesarean deliveries, and 21 percent delivered by cesarean after onset of labor. Ten of the vaginal deliveries were by forceps and 19 by vacuum extraction. Only 169 women were assessed two to five months after delivery.

All measurements showed significant increases in pelvic organ mobility between the third trimester and postpartum visits. These changes were not significantly related to length of gestation, history of induced labor, or duration of the first stage of labor. The increase in pelvic mobility was consistently related to increasing birth weight, but this relationship did not reach statistical significance. The changes were weakly, but significantly, related to the length of the second stage of labor. Postpartum descent on Valsalva maneuver was strongly correlated with type of delivery.

The greatest change was associated with forceps delivery. Cesarean delivery before the onset of labor was associated with an average reduction in bladder neck descent of 2.27 mm, whereas all other forms of delivery were associated with increases ranging from an average of 2.63 mm for stage 1 cesarean delivery to 14.49 mm for forceps delivery.

The authors conclude that vaginal delivery is associated with weakening of pelvic organ support, and this effect is greatest in forceps delivery. The authors’ results confirm the observations from epidemiologic studies that cesarean delivery has a protective effect against pelvic organ prolapse and incontinence later in life.

editor's note: This study should not be interpreted as vindicating “prophylactic” cesarean delivery to prevent pelvic prolapse. In a carefully reasoned editorial,¹ Nygaard and Cruik-shank point out that while some women do avoid urinary symptoms, at least one study indicates that by age 50, women have the same rate of urinary incontinence regardless of delivery mode, and some nulliparous women also develop incontinence with age. Many factors should be taken into consideration when deciding the optimal mode of delivery for a woman. Certainly, widespread use of elective cesarean delivery seems excessive for the estimated 5 to 10 percent reduction in risk of moderate to severe incontinence, especially when weight control and pelvic floor exercises offer alternative means of risk reduction.—a.d.w.