Stress urinary incontinence (SUI), a chronic and debilitating condition, is defined as involuntary loss of urine on physical exertion, sneezing or coughing. The burden is increasingly high in both human and financial terms. SUI symptoms are negatively associated with not only sexual function but mental health .AUA/SUFU guidelines recommend pelvic floor muscle training(PFMT) as the first-line treatment for SUI. PFMT, more commonly known as Kegel exercises, should be done several times a day and need to be conducted consistently over time for benefit to be sustained. However, low compliance often led to poor results. As for surgical correction of SUI, midurethral synthetic slings (MUS) was regarded as an optimal choice with objective cure rates ranging between 83.9% and 100%. Nevertheless, complications including pain, tape erosion and extrusion, and wound infections usually made quality of life (QoL) worse. Thus, patients with SUI who did not want to undergo surgical treatment were more likely to favor other types of conservative therapies.Electrical stimulation (ES) was one of popular conservative therapies and was reported to be an effective treatment. However, it was not often used because of the pain and discomfort caused by percutaneous electrical current.
A few studies reported that magnetic stimulation (MS) was a non-invasive and effective intervention for SUI without obvious side effects, which significantly led urodynamic improvements and a reduction in the frequency of leakage when performing stress test. The mechanism of MS was considered as the same as that of ES, which might not only contract the pelvic floor muscles, but simultaneously inhibit the antagonistic reflex mechanism for emptying the bladder. However, current researches also proposed that MS shown little efficacy on SUI patients. Thus, the safety and efficiency of MS for SUI was still controversial. We, therefore, conducted a systematic review and meta-analysis of the RCTs to evaluate the use of MS.

PubMed, EMBASE and Cochrane library were retrieved for any peer-reviewed original articles in English. Databases were searched up to July 2018. Included studies investigated effects of MS on SUI. The data were analyzed by review manager 5.3 software (Cochrane Collaboration, Oxford, UK).

A total of 4 studies involving 232 patients were identified and included in present meta-analysis. Compared with the sham stimulation, MS group had a significantly less No. of leaks/3days (MD =−1.42; 95%CI: −2.42 to−0.59; P =.007), less urine loss on pad test (gm.)/24h (MD=-4.99; 95%CI: -8.46 to -1.53; P=.005), higher QoL scores (MD =0.42; 95%CI: 0.02 to 0.82; P = .009), and lower ICIQ scores(MD =-4.60; 95%CI: -5.02 to -4.19; P < .001). MS presented a higher improvement cure rate with a significant improvement in both U-UDI scores and the Incontinence Impact Questionnaire Short Form total scores. No MS-related adverse effects were reported in study.

3.1 Characteristics of the included studies
A total of 330 studies were identified based on a defined search strategy. 87 papers were excluded for non-RCTs or non-clinical trials. 26 studies with different base line or different diagnosis or different group setting were also excluded. Finally, 4 studies were eligible for systematic review after critical evaluation.
3.2 Synthesis of results
As is shown in Fig. 2, compared to the sham stimulation, MS group had a significantly less No. of leaks/3days (MD =−1.42; 95%CI: −2.42 to−0.59; P =.007) , less urine loss on pad test (gm.)/24h (MD=-4.99; 95%CI: -8.46 to -1.53; P=.005) , higher QoL scores (MD =0.42; 95%CI: 0.02 to 0.82; P = .009) , and lower ICIQ scores(MD =-4.60; 95%CI: -5.02 to -4.19; P < .001) . No publication bias was recorded in study .
The improvement rates in Fujishiro et al in MS and sham group were 74% and 32%, respectively. In Lim et al, the improvement rate was 60% in the experimental group compared to 15% in the control group. Studies reported no MS-related adverse effects.

In the short-term follow-up, MS significantly improved the symptoms of SUI, reduced the No. of leaks/3days and the daily loss of urine, with lower ICIQ scores and significantly improved QoL. Although the beneficial effects of MS are temporary and not an alternative to surgical treatment, it can be considered as a conservative and noninvasive treatment approach in the management of SUI in patients not available for surgery.