There is good evidence that postnatal pelvic floor exercises are effective in the treatment of postpartum stress incontinence 7,13,14 . Few studies exist using antenatal pelvic floor exercises 15,16 despite the possibility that these might be effective in preventing postnatal stress incontinence 5 . The aim of this study was to assess the effect of supervised antenatal pelvic floor exercises in the prevention of postpartum stress incontinence in this at risk group with bladder neck mobility. A randomised, controlled trial was carried out on primigravidae with bladder neck mobility as previously defined 12 . Local ethical approval was granted. Written, fully informed consent was obtained from all participants.
METHODSAll primigravidae attending the antenatal clinic of a NHS Trust Hospital with 4500 deliveries per year were invited to have a perineal ultrasound scan to measure bladder neck mobility at approximately 20 weeks of gestation. Measurement of bladder neck mobility was as previously described 12,17 . The women were positioned sitting upright with their feet in stirrups. Using an ultrasound scanner (Pie Medical Scanner 100, Maastricht, The Netherlands) with a 5MHz curvilinear probe, images were taken at rest and with a standardised Valsalva manoeuvre. As in the previous study 12 , the women were asked to blow into a modified sphygmomanometer to a pressure of 30mmHg, which corresponds to approximately 40cm H 2 O. Those with a bladder neck mobility of more than 5mm on linear movement following standardised valsalva were invited to take part in the study. For a sample of the patients repeat measurements were made on each of these patients by the same observer and by a separate observer to obtain measures of intra and inter-observer error. Exclusion criteria were any pre-pregnancy urinary incontinence or neurological disorder.Patients were then randomised to either supervised pelvic floor exercises with a physiotherapist (F.P.) during the antenatal period, or to a control group. A separate sample of 20 subjects was used to obtain measures of reproducibility for bladder neck mobility measurements.