Urinary and faecal incontinence are associated with childbirth, but the pathophysiological origins of these problems are poorly understood. Charlotte Chaliha and her colleagues (pages 1354–1359) performed detailed urodynamic investigations in 161 nulliparae before and after delivery to establish the basic physiology of bladder function during pregnancy and after childbirth. The authors found significant changes in several urodynamic variables postnatally, consistent with the relief of intra-abdominal pressure after childbirth. These findings are not unexpected; however the important results of this study are the relationships of the method of delivery to the postnatal urodynamic tests. There was no difference in bladder function in women who had a spontaneous vaginal delivery, an instrumental vaginal delivery or a caesarean section; and there was no association with urodynamic variables and the duration of the passive second stage of labour, duration of the active second stage of labour, birthweight, the circumference of the infant's head, epidural analgesia, perineal trauma, augmentation of labour or postnatal catheterisation of the bladder.

In a similar study Sylvain Meyer and his colleagues (pages 1360–1365) investigated the effects of forceps and spontaneous vaginal delivery on urethral sphincter and pelvic floor function in 107 nulliparae. Epidural analgesia was performed more commonly in women delivered by forceps, who also underwent episiotomy more often; but there was no difference in birthweight, head circumference of the infant and duration of the second stage of labour. There was no difference in the position of the bladder neck when evaluated by transperineal ultrasound; and no difference in urethral sphincter function. However women delivered by forceps had much weaker muscles of the pelvic floor on objective testing; and a much greater decrease in intra-anal pressure on squeezing compared with the values before delivery.

These studies are reassuring, for they suggest that the supposed trauma of instrumental vaginal delivery on the bladder neck does not exist; however the study by Meyer and colleagues confirms the harmful effects of forceps delivery on the posterior compartment of the pelvic floor.