Pelvic floor disturbance after childbirth: vaginal delivery damages the upper levels of sphincter innervation.

PURPOSE

Vaginal delivery disturbs pelvic floor innervation, which has previously been studied as a single mechanism. The effects of childbirth on innervation at different levels of the anal sphincter system were studied after childbirth.

METHODS

Both anal manometry and motor latencies were measured in 67 females. Twenty-nine females (30.8 +/- 4.4 years) were examined four days after vaginal delivery. Eleven of these 29 females were re-examined five months after vaginal delivery. Nineteen females (33.6 +/- 4.6 years) who were examined five to nine days after undergoing an elective cesarean section and 19 asymptomatic, nonpregnant females (26.8 +/- 6.9 years) served as controls. Motor latencies were bilaterally measured within the anal sphincter system at 5, 3.8, 2.6, and 1.5 cm from the perineal skin by using a concentric needle electrode after sacral magnetic stimulation. Means of the bilateral latencies were analyzed.

RESULTS

In postpartum females who gave birth vaginally, motor latencies at 5 and 3.8 cm, although not those at 2.6 and 1.5 cm, from the perineal skin were significantly prolonged, and anal pressure monitored by maximum resting and squeeze pressures was significantly decreased compared with that in control females. The decreased anal pressure normalized spontaneously. The prolonged motor latencies at the upper two levels of the anal sphincter system persisted in these females for five months after vaginal delivery.

CONCLUSIONS

The disturbance of innervation of the upper anal sphincter system after vaginal delivery may last for a long time, whereas the decreased anal pressure normalizes in a short time. The protracted disturbance of innervation of the upper anal sphincter system may be associated with later development of fecal incontinence.