BACKGROUND:About one-third of women have urinary incontinence (UI) and up to one-tenth have faecal incontinence (FI) after childbirth. Pelvic floor muscle training (PFMT) is commonly recommended during pregnancy and after birth for both preventing and treating incontinence. This is an update of a Cochrane Review previously published in 2017. OBJECTIVES:To assess the effects of PFMT for preventing or treating urinary and faecal incontinence in pregnant or postnatal women, and summarise the principal findings of relevant economic evaluations. SEARCH METHODS:We searched the Cochrane Incontinence Specialised Register, which contains trials identified from the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, MEDLINE In-Process, MEDLINE Epub Ahead of Print, CINAHL, ClinicalTrials.gov, WHO ICTRP, and handsearched journals and conference proceedings (searched 7 August 2019), and the reference lists of retrieved studies. SELECTION CRITERIA:We included randomised or quasi-randomised trials in which one arm included PFMT. Another arm was no PFMT, usual antenatal or postnatal care, another control condition, or an alternative PFMT intervention. Populations included women who, at randomisation, were continent (PFMT for prevention) or incontinent (PFMT for treatment), and a mixed population of women who were one or the other (PFMT for prevention or treatment). DATA COLLECTION AND ANALYSIS:We independently assessed trials for inclusion and risk of bias. We extracted data and assessed the quality of evidence using GRADE. MAIN RESULTS:We included 46 trials involving 10,832 women from 21 countries. Overall, trials were small to moderately-sized. The PFMT programmes and control conditions varied considerably and were often poorly described. Many trials were at moderate to high risk of bias. Two participants in a study of 43 pregnant women performing PFMT for prevention of incontinence withdrew due to pelvic floor pain. No other trials reported any adverse effects of PFMT. Prevention of UI: compared with usual care, continent pregnant women performing antenatal PFMT probably have a lower risk of reporting UI in late pregnancy (62% less; risk ratio (RR) 0.38, 95% confidence interval (CI) 0.20 to 0.72; 6 trials, 624 women; moderate-quality evidence). Antenatal PFMT slightly decreased the risk of UI in the mid-postnatal period (more than three to six months' postpartum) (29% less; RR 0.71, 95% CI 0.54 to 0.95; 5 trials, 673 women; high-quality evidence). There was insufficient information available for the late postnatal period (more than six to 12 months) to determine effects at this time point (RR 1.20, 95% CI 0.65 to 2.21; 1 trial, 44 women; low-quality evidence). Treatment of UI: compared with usual care, there is no evidence that antenatal PFMT in incontinent women decreases incontinence in late pregnancy (very low-quality evidence), or in the mid-(RR 0.94, 95% CI 0.70 to 1.24; 1 trial, 187 women; low-quality evidence), or late postnatal periods (very low-quality evidence). Similarly, in postnatal women with persistent UI, there is no evidence that PFMT results in a difference in UI at more than six to 12 months postpartum (RR 0.55, 95% CI 0.29 to 1.07; 3 trials; 696 women; low-quality evidence). Mixed prevention and treatment approach to UI: antenatal PFMT in women with or without UI probably decreases UI risk in late pregnancy (22% less; RR 0.78, 95% CI 0.64 to 0.94; 11 trials, 3307 women; moderate-quality evidence), and may reduce the risk slightly in the mid-postnatal period (RR 0.73, 95% CI 0.55 to 0.97; 5 trials, 1921 women; low-quality evidence). There was no evidence that antenatal PFMT reduces the risk of UI at late postpartum (RR 0.85, 95% CI 0.63 to 1.14; 2 trials, 244 women; moderate-quality evidence). For PFMT started after delivery, there was uncertainty about the effect on UI risk in the late postnatal period (RR 0.88, 95% CI 0.71 to 1.09; 3 trials, 826 women; moderate-quality evidence). Faecal incontinence: eight trials reported FI outcomes. In postnatal women with persistent FI, it was uncertain whether PFMT reduced incontinence in the late postnatal period compared to usual care (very low-quality evidence). In women with or without FI, there was no evidence that antenatal PFMT led to a difference in the prevalence of FI in late pregnancy (RR 0.64, 95% CI 0.36 to 1.14; 3 trials, 910 women; moderate-quality evidence). Similarly, for postnatal PFMT in a mixed population, there was no evidence that PFMT reduces the risk of FI in the late postnatal period (RR 0.73, 95% CI 0.13 to 4.21; 1 trial, 107 women, low-quality evidence). There was little evidence about effects on UI or FI beyond 12 months' postpartum. There were few incontinence-specific quality of life data and little consensus on how to measure it. AUTHORS' CONCLUSIONS:This review provides evidence that early, structured PFMT in early pregnancy for continent women may prevent the onset of UI in late pregnancy and postpartum. Population approaches (recruiting antenatal women regardless of continence status) may have a smaller effect on UI, although the reasons for this are unclear. A population-based approach for delivering postnatal PFMT is not likely to reduce UI. Uncertainty surrounds the effects of PFMT as a treatment for UI in antenatal and postnatal women, which contrasts with the more established effectiveness in mid-life women. It is possible that the effects of PFMT might be greater with targeted rather than mixed prevention and treatment approaches, and in certain groups of women. Hypothetically, for instance, women with a high body mass index (BMI) are at risk of UI. Such uncertainties require further testing and data on duration of effect are also needed. The physiological and behavioural aspects of exercise programmes must be described for both PFMT and control groups, and how much PFMT women in both groups do, to increase understanding of what works and for whom. Few data exist on FI and it is important that this is included in any future trials. It is essential that future trials use valid measures of incontinence-specific quality of life for both urinary and faecal incontinence. In addition to further clinical studies, economic evaluations assessing the cost-effectiveness of different management strategies for FI and UI are needed.