Effect of postpartum pelvic floor muscle training in prevention and treatment of urinary incontinence: a one-year follow up

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1 British Journal of Obstetrics and Gynaecology August 2000, V01107, pp Effect of postpartum pelvic floor muscle training in prevention and treatment of urinary incontinence: a one-year follow up Siv M~rkved Research Fellow, Kari B@ Professor Departments of Physiotherapy; and Gynaecology and Obstetrics, Regional Hospital, TrondheimLMelhus Physiotherapy Clinic, Melhus, Norway; Norwegian University of Sport and Physical Education, Oslo, Norway Objective To evaluate the long term effect of a postpartum pelvic floor muscle training course in prevention and treatment of urinary incontinence. Design A prospective matched controlled trial. Sample and methods All women who had participated in a matched controlled study evaluating the effect of an eight-week pelvic floor muscle training program in prevention and treatment of urinary incontinence in the immediate postpartum period were contacted by telephone one year after delivery. They were invited to participate in a follow up study. The study group consisted of 81 matched pairs (n = 162), with a mean age (range) 28 years (19-40), and mean number (range) of deliveries 1.8 (1-5). Seventy-six pairs had normal vaginal deliveries and five elective caesarean sections. Registration of continence status was by structured interview and a standardised pad test. Clinical assessment of pelvic floor muscle function and strength were by vaginal palpation and vaginal squeeze pressure. Main outcome measure Stress urinary incontinence. Results At the one year follow up, significantly more women in the former control group than in the training group reported stress urinary incontinence andor showed urinary leakage at the pad test (P < 0.01). A significantly greater (P < 0.01) muscle strength increase in the period between 16th week and one year postpartum was demonstrated in the former training group (mean 4.4 cm H, 0,95% CI ) than in the control group (mean 1.7 cm H2 0,95% CI ). Conclusion This one year follow up study demonstrates that a specially designed postpartum pelvic floor muscle training course was effective in the prevention and treatment of stress urinary incontinence. The benefits from pelvic floor muscle training are still present one year after delivery. INTRODUCTION In order to restore function in the pelvic floor muscles after childbirth, women in most industrial countries have been encouraged to perform pelvic floor muscle exercises. Pregnancy and vaginal delivery have been considered main risk factors in the development of stress urinary in~ontinencel-~. Wilson et a1.4 found that urinary incontinence appeared to be a common problem three months after giving birth, affecting more than 34% of the women in a sample containing both primiparae and multiparae. Morkved and BZ5 reported an incontinence rate of 42% during pregnancy. Two months after delivery, the number of women with urinary incontinence (38%) was nearly the same as during pregnancy. Correspondence: Dr S. Mgirkved, Norwegian University of Science and Technology, Department of Community Medicine and General Practice, N-7489 Trondheim, Norway. The theoretical basis for pelvic floor muscle exercise to treat and prevent stress urinary incontinence is based on the muscular changes that may occur after specific strength training'. This change is supposed to be neural adaptation during the first six to eight weeks and muscle hypertrophy after a further period of strength training7. A strong and well-functioning pelvic floor can build a structural support for the bladder and the urethra. In addition, a well-timed, fast and strong contraction may prevent urethral decent and close the urethra during an abrupt intra-abdominal pressure rise'. Postpartum pelvic floor muscle training has been demonstrated to be effective in prevention and treatment of stress urinary incontinence in the immediate postpartum period8. In an initial study' Mflrkved and BZ concluded that, between the 8th and 16th week after delivery, a specially designed postpartum pelvic floor muscle training course was effective in increasing pelvic floor muscle strength and reducing urinary incontinence RCOG 2000 British Journal of Obstetrics and Gynaecology

2 EFFECT OF PELVIC FLOOR MUSCLE TRAINING 1023 In the group of women attending the eight-week pelvic floor muscle training course, 66% were cured immediately after secession of the supervised training period, compared with 33% in the control group. The results also showed that the success of postpartum pelvic floor muscle exercise depended on training frequency and intensity. However, there is a lack of knowledge concerning the long term effect of postpartum pelvic floor muscle training. We have not found any follow up study addressing this item, neither are the optimal frequency and intensity for maintaining pelvic floor muscle strength known. The aim of the present study therefore was to evaluate the long term effect of the previously published8 postpartum pelvic floor muscle training course. METHODS All women, who had participated in a matched controlled trial8, which assessed the effect of an eight-week pelvic floor muscle training program in prevention and treatment of urinary incontinence in the immediate postpartum period, were contacted by telephone one year after delivery. They were invited to participate in a follow up study, including interview and clinical assessment of pelvic floor muscle function and strength. For practical and economical reasons, the individuals who undertook the assessments were not blinded with respect to the previous studys. In the original studys a prospective comparison design, comprising 99 matched pairs of mothers, was used. The criteria for matching were age (2 years), parity (1,2,3,4 c deliveries) and type of delivery (e.g. normal vaginal, forceps, vacuum, elective caesarean section). All women in a particular Norwegian community, who were delivered at the local hospital during a one-year period, were assigned to the study s training group. A matched control group was comprised of women from a neighbouring, socioeconomically comparable community, who were delivered at the same hospital within the same period. The training group followed a specially designed pelvic floor muscle exercise course9 between 8th and 16th week after delivery, training with a physiotherapist in groups of five to ten participants for 45 minutes once a week, and daily exercises at home for a period of eight weeks. The physiotherapist encouraged the participants to perform two series of eight to twelve maximum contractions and to hold the contraction for 6-8 s. At the end of each contraction, three to four fast contractions were added. Participant motivation was strongly emphasised by the physiotherapist. In addition, they were asked to follow a home training program the first six months after delivery. Frcquency of exercise was recorded in a training diary. The control group received the customary written postpartum instructions from the hospital. They were not discouraged from performing pelvic floor muscle exercise on their own. Across the time of the study, several physical and social constraints resulted in some women being unable to continue. One year after the birth 180 of the mothers agreed to participate in the follow up test. Because the number of matched pairs attending the one-year follow up varied from the number in the original study8, all longitudinal changes in pelvic floor muscle strength and continence status were conducted using a constant sample, including the 81 matched pairs that attended all tests. Hence, the study group consisted of 81 matched pairs (n = 162), mean age (range) 28 years (19-40) and mean number (range) of deliveries 1.8 (1-5). Seventysix pairs had normal vaginal deliveries and five elective caesarean sections. Before the intervention started eight weeks postpartum, there was no difference between the groups according to the number of women with stress urinary incontinence: 34 women in the training group and 36 women in the control group reported stress urinary incontinence. Sixteen weeks postpartum the difference between the groups was statistically significant (P < 0.05): 13 women in the training group and 24 women in the control group reported stress urinary incontinence. The regional medical ethics committee approved the study. Evaluation One year after delivery all subjects were asked about their continence status. Urinary incontinence was,registered both in accordance to the International Continence Society s definition and in a more general term. The question was Do you leak urine at any time: never, seldom, weekly or daily? They were told to describe the situations in which urine was leaked, and they were asked about breastfeeding, menstruation, participation in physical activities, and pelvic floor muscle training in the period between the test 16 weeks after delivery and the one-year follow up test. All participants performed a standardised test, designed for the initial study8. After voiding, the women drank 1 L of water within 30 minutes. They wore a preweighed pad and jumped up and down for 30 s, jumped with legs in alternate abduction and adduction for 30 s and coughed three times. After the test the participants voided, the volume was measured, and the pad was weighed. The cut off point for a positive pad test was 2 g. Two instruments, designed to measure how women perceive stress urinary incontinence and tested for reproducibi1ityl0, were used before and after treatment. The leakage index is a five-point scale (1 = never, 5 = always) containing 13 types of physical exertions known to trigger urinary leakage. The social activity

3 1024 S. M0RKVED & K. B0 index contains nine social settings in which women may have problems to participate. For each characteristic, a 10 cm visual analogue scale (0 = impossible to participate, 10 = no problem to participate) was used. Vaginal palpation was used to assess the women s ability to perform pelvic floor muscle contraction. The women were in a supine position with straight legs. One finger was used for palpation. No observable synergistic contraction of hip adductors, glutei s or rectus abdominis was accepted. A vaginal balloon catheter (balloon size 6.7 x 1-7 cm), connected to a pressure transducer (Camtech Ltd, 1300 Sandvika, Norway), was used to measure vaginal pressure during pelvic floor muscle contractions. Positioning was with the middle of the balloon 3-5 cm inside the introitus vagina. Only contractions with observed inward movement of the balloon catheter were accepted. The method has been found to be reliable and valid. Statistical analysis Except for frequencies, all results are given as mean values with 95% confidence intervals (CI). Categorical data were analysed by x test (Tables 1, 3 and 5). As several.o 5i- 16th week postpartum I 8 1 year postpartum Fig. 1. Pelvic floor muscle strength measured by vaginal squeeze pressure (cm H,O) in the training and control groups at the 16th week and one year postpartum. Mean and 95% confidence interval. I variables were not normally distributed, the Wilcoxon matched pairs test was used to test the differences within and between the two groups of matched pairs (Fig. 1.). The Mann-Whitney two sample test was used to test the differences between independent groups of different sample sizes (Tables 2 and 4). P values c 0.05 were considered significant. RESULTS Table 1 shows background variables. In the period between 16th week and one year after delivery the women in the former training group exercised the pelvic floor muscles more frequently than the control group. Between the two tests 53% of the women in the former training group, and 30% in the control group had exercised the pelvic floor muscle no less than three times per week. Analyses with Wilcoxon matched pairs test showed a significantly greater increase in muscle strength (Pc 0.001) in the period between the 16th week and one year after giving birth, in the former training group (mean 4.4 cm H2 0; 95% CI ), than in the control group (mean 1-7 cm H,O, 95% CI ) (Fig. 1). Table 2 shows changes in pelvic floor muscle strength according to frequency of pelvic floor muscle training in the training group and the control group. The change in pelvic floor muscle strength was significantly (P c 0.02) related to frequency of pelvic floor muscle training only in the training group. When comparing all women in both groups performing pelvic floor muscle training three times per week or more, and the women performing fewer pelvic floor muscle exercises, the change in pelvic floor muscle strength was significantly (P c 0.001) greater in those who had exercised three times per week or more. The number of women with stress urinary incontinence registered by structured interview and/or pad test is shown in Table 3. There was a statistically significant difference (P c 0.03) in urinary leakage assessed by the pad test between the groups, both 16 weeks postpartum and at the 12-month follow up. Five women in the training group compared with 14 women in the control group showed urinary leakage at the pad test at 12 month. Table 1. Background variables in the training group (TG) and the control group (CG). Values are given as n (a), unless otherwise indicated. Background variables: frequencies TG (n = 81) CG (n = 81) P* Breastfeeding one year postpartum 23 (28%) 32 (40%) Menstruation one year postpartum 74 (91%) 78 (96%) Leisure physical activity between 16th week and one year postpartum 43 (53%) 46 (57%) Pelvic floor muscle exercise between 16th week and one year postpartum 43 (53%) 24 (30%) *x2 test. Q RCOG 2000 Br J Obstet Gynaecol 107,

4 ~ ~~ EFFECT OF PELVIC FLOOR MUSCLE TRAINING 1025 Table 2. The effect of frequency of pelvic floor muscle (PFM) training on changes in PFM strength between 16th week and one year after delivery, in the training group, the control group, and both groups together. Values are given as mean [95% CI], unless otherwise indicated. TG = training group; CG = control group. Change in PFM strength (cm H,O) PFM training c 3 times per week PFM training 3 times per week P* TG 2.7 [1.144] 5.9 [4*2-7.6] (n = 38) (n = 43) CG 1.1 [ [144.9] (n = 57) (n = 24) Both groups 1 *8[ ] 4.9 [ ] (n = 95) (n = 67) *Mann-Whitney test. Among these women, one woman in the training group and six women in the control group had not reported stress urinary incontinence at the structured interview. Pelvic floor muscle strength in incontinent and continent women in both groups is shown in Table 4. When comparing all continent and incontinent women in both groups, median pelvic floor muscle strength was significantly (P < 0.01) greater in the group of continent women. Sixteen weeks postpartum significantly (P < 0.05) fewer women in the training group than in the control group reported urinary leakage. The difference was persistent at the 12-month follow up (Table 5). The data of the 13 women in the training group who reported having urinary incontinence 16 weeks postpartum were studied in more detail to detect whether a prolonged exercise period could improve the results. Eight of these women were cured one year after giving birth, six of whom after a prolonged training period. The remaining five were still incontinent after one year. None of these five women had followed the home training program after cessation of organised and supervised pelvic floor muscle training. A detailed study of the additional eight women reporting urinary incontinence one year after delivery shows that four of them were incontinent at the time they entered the study (eight weeks postpartum); however, they were cured immediately after the training period (16 weeks postpartum). Table 3. Number of women with stress urinary incontinence registered by structured interview and/or pad test, in the training group (TG) and the control group (CG) at the tests 16 weeks and one year postpartum. Values are given as n (%), unless otherwise indicated. TG CG Urinary incontinence: frequencies (n = 81) (n = 81) P* 16th week postpartum 13(16) 25 (31) One year postpartum 14(17) 31 (38) *x2 test. Table 4. Pelvic floor muscle (PFM) strength one year after delivery, in women with stress urinary incontinence (incontinent) and women without stress urinary incontinence (continent) registered by self report and/or pad test, in the training group, the control group, and both groups together. Values are given as mean [95% CI], unless otherwise indicated. TG = training group; CG = control group. PFM strength (cm H,O) Incontinent Continent P* TG 17.9 [ *9] 22.2 [ ] CG (n = 14) 11.7 [9.2-14*1] (n = 67) 14.8 [ ] Both PUPS (n = 31) 14.6 [ *1] (n = 50) 19.9 [ ] 0@028 (n = 45) (n = 117) *Mann-Whitney test. Four women reported the onset of urinary incontinence in the period between 16th week and one year postpartum. No statistical significant difference between groups was demonstrated, measured by the leakage index and the social activity index. DISCUSSION The results demonstrate that a significant reduction in prevalence of stress urinary incontinence and increase in pelvic floor muscle strength was maintained one year after delivery in a group of women following an eight-week intensive exercise course between the 8th and 16th week after giving birth, compared with a matched control group. The initial training group had trained more frequently and more intensively than the control group. This group demonstrated significantly greater improvement in pelvic floor muscle strength both 16 weeks after delivery and when they were tested one year postpartum (Fig. 1). This indicates that strength training of the pelvic floor muscles has to be intensive to be effective, in agreement with the results of studies on genuine stress incontinent women9j3j4.

5 1026 S. MORKVED & K. B0 Table 5. Number of women with stress urinary incontinence (SUI) registered in the structured interview in the training group (TG) and the control group (CG) at the tests 16 weeks and one year postpartum. Values are given as n (%), unless otherwise indicated. TG CG SUI frequencies (n = 81) (n = 81) P* 16th week postpartum 13 (16) 24(30) < Once per week 12 (15) 17 (21) < Daily once per week 0 (0) 7 (9) Daily 1(1) 0 (0) One year postpartum 13 (16) 25 (31) < Once per week 9(11) ls(22) < Daily once per week 3 (4) 7 (9) Daily 1(1) 0 (0) *x2 test. The significant reduction in the number of women with stress urinary incontinence in the training group in the initial study shows that in most women postpartum urinary incontinence may be treated successfully with intensive pelvic floor muscle exercises8. However, some of the women in the training group still were incontinent 16 weeks postpartum and at the one-year follow up. It is worth considering why the exercises did not prevent urinary incontinence or cure it in all women in this group. The training period in the initial studye was only eight weeks, and therefore neural adaptation (i.e. more effective motor units and increased frequency of excitation) probably caused the increase in pelvic floor muscle strength. Pelvic floor muscle strength training may have caused more effective action of the reminding motor units in the pelvic floor muscles, and thereby cured incontinence in 67% of the participants reporting urinary incontinence in the training group. In the 13 participants reporting persistent urinary incontinence at the test 16 weeks after delivery, a prolonged training period may have improved the results. Hypertrophy of the muscle fibres is a slow process, needing regular and intense strength training for more than eight weeks7. With increased resistance training, hypertrophy may continue for years, and a long training period is therefore needed to increase the muscle volume. The data showed that eight of the incontinent women were cured one year postpartum, six of them after a prolonged exercise period. The five women with incontinence 16 weeks after delivery were still incontinent at the oneyear follow up. None of these women had followed the training program after completing the period of supervised training, and neither had the eight additional women reporting urinary incontinence at the one-year follow up test. Therefore, the question as to why the exercises did not prevent urinary leakage or cure it in all women in the training group may be due to a too short period of intensive pelvic floor muscle exercise. However, there was no statistically significant difference in the median pelvic floor muscle strength between the continent and incontinent women in the training group. In contrast, there was a statistically significant difference in pelvic floor muscle strength between continent and incontinent women in the control group. The results in the training group may be due to type I1 error, because of the small numbers, or it may indicate that the compensatory effect of strong pelvic floor muscle^'^ was not enough to ensure continence in all women. Follow up urodynamic studies may have detected whether the leakage was due to intrinsic sphincter deficiency or urethral hypermobility. Other possible explanations why some of the participants in the training group still was incontinent one year after delivery may be severe damage to the pelvic floor during delivery (e.g. peripheral nerve damage or rupture of muscle fibres andor connective tissues3,16,17 or over-stretching of supporting ligaments *). At the one-year follow up, pelvic floor muscle strength had improved from the test at the 16th week postpartum in both groups. However, in the control group the improvement was significantly less than in the former training group. The improvement in pelvic floor muscle strength in the control group probably reflects either that a great number of the participants in the control group reported practice of pelvic floor muscle exercise or it reflects a normal reparative process. This is consistent with other researchers suggestion^'^^^^. However, this gain in pelvic floor muscle strength did not seem to be sufficient in prevention and treatment of stress urinary incontinence. The optimal frequency and intensity for maintaining pelvic floor muscle strength is not known. DiNubile states that, in skeletal muscles, there is a reversal of strength in instances of sub-maximum or minimal stimulation after training cessation. However, once satisfactory levels of muscle strength have been attained, the results may be maintained with a reduced training frequency of two exercise sessions per week. Also Graves et d2 found that muscle strength might be maintained for short periods of time with a training frequency of once per week as long as the intensity is kept constant. In the present study there was a difference in the number of women with urinary incontinence registered by self-reporting and objectively assessed by the pad test. The validity and reproducibility of the registration and evaluation methods used can be questioned. With respect to self-reporting, the women s daily life experiences with urinary incontinence were registered. During daily life women may experience a variety of situations that trigger urinary leakage even more than performing the stress test (pad test). The pad test was not performed with a standardised bladder volume. According to Lose et ~ 1 and. Kraj123, ~ ~ tests without standardised bladder volume are less reproducible. 0 RCOG 2000 Br J Obstet Gynaecol 107,

6 The results of the leakage index showed no statistically significant change between the groups. Also, the social activity index indicated that the perceived urinary leakage had very little influence on these women s participation in the social activities mentioned. The instruments used have been tested and found to be reproducible 0. Nevertheless, some of the questions being used may be less useful for women during the first year after delivery. In Norway women have full salary to stay at home with their babies the fnst 12 months after childbirth. None of the participants had therefore gone back to work, and many women had not attended all the social situations in the questionnaire at the time of this investigation. This might have influenced the results. The results of the leakage and social activity index may also be reflected by the relative moderate degree of leakage shown in the pad test. As far as can be ascertained, only one previous long term study documenting the effect of postpartum pelvic floor muscle exercise has been published24. Wilson and Herbi~on~~ reported a significantly lower prevalence of urinary incontinence in a group of women who performed postpartum pelvic floor muscle exercises compared with a control group. However, there was no significant difference between the groups in perineometer readings. A high dropout rate may have flawed the results of the mentioned A lack of statistically significant difference in pelvic floor muscle strength between a pelvic floor muscle training group and a control group was also reported by Sampselle et dz0. However, they had a high dropout and ended up comparing the muscle strength in ten and six women; the negative results most likely were due to type I1 error. Because the training period, training protocol, adherence rates, and the evaluation methods are different, it is difficult to compare the results of previous studies with the present study. Women in the postpartum period seem to need strong motivation and close follow up if exercise is to be maximally effective. This is consistent with findings reported by Ashworth and HaganZ5. They analysed the social consequences of noncompliance with pelvic floor muscle exercise and reported that women told to train the pelvic floor muscles found that the exercises were not personally salient and not easily adopted as a personal project. The exercises focus on an area of the body which is not easy to control consciously. There seems to be a need for more studies addressing pregnant women and the health of new mothers in general. A study by Brown and Lumley26 showed that many of the problems which occur commonly in the postnatal period (e.g. urinary incontinence, painful perineum, haemorrhoids, sexual problems, relationship difficulties, and depression) are not easy subjects for women to disclose. Despite a high rate of consultation with general EFFECT OF PELVIC FLOOR MUSCLE TRAINING 1027 practitioners in the first six postnatal months, a majority of the women in their study did not recall discussing their own health at these visits. Kline et al2 reported that women often felt poorly prepared for the postpartum period in part because functional health consequences are not well understood. They suggested that maternal functional health might be decreased for months after delivery, even among uncomplicated patients. A significant public health issue therefore would be to build strategies for encouraging women to talk about postpartum morbidity, and search for effective prevention and treatment strategies. It is essential that future services for women after childbirth should be organised according to results from controlled clinical trials. In conclusion, this one year follow up study demonstrates that a specially designed eight-weeks postpartum pelvic floor muscle training course was effective in the prevention and treatment of stress urinary incontinence. The benefits from pelvic floor muscle training are still present one year after delivery. Acknowledgements Financial support was given by The Norwegian Fund for Postgraduate Training in Physiotherapy and the Norwegian Board of Health. References 1 Allen RE, Hosker GL, Smith ARB, Warell DW. Pelvic floor damage and childbirth: a neurophysiological study. Br J Obstet Gynaecol 1990; 97: Snooks SJ, Swash M, Setchell M, Henry MM. Injury to innervation of pelvic floor sphincter musculature in childbirth. Lancet 1984; ii: Snooks SJ, Swash M, Mathers SE, Henry MM. Effect of vaginal delivery on the pelvic floor: a five year follow-up. Br J Surg : Wilson PD, Herbison RM, Herbison GP. Obstetric practice and the prevalence of urinary incontinence three months after delivery. Br J Obstet Gynaecoll996; 103: Markved S, B0 K. Prevalence of urinary incontinence during pregnancy and postpartum. Int Urogynecol J 1999; 10: Be K. Pelvic floor muscle exercise for the treatment of stress urinary incontinence. An exercise physiology perspective. Inr Urogynecol J 1995; DiNubile NA. Strength training. Clin Sports Med 1991; Markved S, B6 K. The effect of postpartum pelvic floor muscle exercise in the prevention and treatment of urinary incontinence. Int Umg- ynecol J 1997; 8: Ba K, Hagen RH, Kvarstein B, J~irgensen J, Wen S. Pelvic floor muscle exercise for the treatment of female stress urinary incontinence. In. Effects of two different degrees of pelvic floor muscle exercises. Neurouml Umdyn 19909: Be K. Reproducibility of instruments designed to measure subjective evaluation of female stress urinary incontinence. Scand J Urol Nephroll994; 28: Be K, Hagen RH, Kvarstein B, Larsen S. Pelvic floor muscle exercise for the treatment of female stress urinary incontinence 11. Validity of vaginal pressure measurements of pelvic floor muscle strength. The necessity of supplementary methods for control of correct contraction. Neumurol Urodyn 1990; 9: Altman DG. Practical statistics for medical research. Chapman and Hall, London: 1991.

7 1028 S. MORKVED & K. B 8 13 Wilson PD, Sammarai TAL, Deakin M, Kolbe E, Brown ADG. An objective assessment of physiotherapy for female genuine stress incontinence. Br J Obstet Gvnaecoll987; 94: Be K, Talseth T, Holme I. Single blind, randomised controlled trial of pelvic floor exercises, elecbical stimulation, vaginal cones, and no treatment in management of genuine stress incontinence. BMJ 1999; DeLancey JOL. Stress urinary incontinence: where are we now, where should we go?am JObstet Gynecoll996; 175: Sayer TR, Dixon JS, Hosker GL, Warell DW. A study of periurethral connective tissue in women with stress incontinence of urine. Neurourol Urodyn 1990; Landon CR, Crofts CE, Smith ARB, Trowbridge EA. Mechanical properties of fascia during pregnancy: a possible factor in the development of stress incontinence of urine. Contemp Rev Obstet Gynaecol 1990; Ulmsten U, Ekman G, Giertz G, Malmstrom A. Different biochemical composition of connective tissue in continent and stress incontinent women. Acta Obstet Gynecol Scad 1987; 66: Peschers UM, Schaer GN, DeLancey JOL, Schuessler B. Levator ani function before and after childbirth. Br J Obster Gynaecol 1997; 104: Sampselle CM, Miller JM, Mims BL, DeLancey JOL, Ashton-Miller JA, Antonakos CL. Effect of pelvic muscle exercise on transient incontinence during pregnancy and after birth. Obstet Gynecol 1998; 91: Graves JE, Pollock ML, Leggett SH, Braith RW, Carpenter DM, Bishop LE. Effect of reduced training frequency on muscular strength. Inr JSports Med 1988; Lose G, Rosenkilde P, Gammelgaard J, Schroeder T. Pad weighing test performed with standardized bladder volume. Urology 1988; 32: Krajl B. Comparative study of pad tests: reliability and repetitiveness. Neurourol Urodyn 1989; 8: Wilson PD, Herbison GP. A randomised controlled trial of pelvic floor muscle exercises to treat postnatal urinary incontinence. Int Urogynecol J 1998; 9: Ashworth PD, Hagan MT. Some social consequences of non-compliance with pelvic floor exercises. Physiotherapy 1993; 79: Brown S, Lumley J. Maternal health care after childbirth: results of an Australian population based survey. Br J Obster Gynaecoll998; 105: Kline CR, Martin DP, Deyo RA. Health Consequences of Pregnancy and Childbirth as Perceived by Women and Clinicians. Obstet Gynecoll998; 92: Accepted 5 April 2000