The effect of vaginal delivery on anal function

The commonest cause of faecal incontinence is considered to be childbirth. In this review we consider the available data on the prevalence of faecal i ncontinence in the community and the incidence of incontinence after childb irth. The results and implications of studies on childbirth using anal mano metry, neurophysiological tests and anal ultrasound are discussed. The deve lopment of symptoms are more likely with a third degree tear and forceps de livery. Reduced resting and squeeze pressures are seen early after vaginal delivery with recovery noted with time. Reduced pressures have been seen in symptomatic and asymptomatic women and there is no correlation of the pres sures with the presence or absence of a sphincter defect or evidence of pud endal neuropathy. Anal manometry can not be used as an indication of muscle or nerve injury. Both sphincter defects and evidence of pudendal neuropath y are common after vaginal delivery but these are not necessarily associate d with symptoms. It is suggested that such occult sphincter injuries may go on to be symptomatic in later life. The number of these injuries, however, is far greater than the documented prevalence of incontinence in the commu nity, and hence many must remain asymptomatic. Their true clinical signific ance remains uncertain.