effect of foeniculum vulgare on primary dysmenorrhea: a systematic review and meta-analysis

Context: dysmenorrhea is a common problem in women. objectives: this study aimed to summarize the results of all relevant clinical trials to draw a conclusion regarding the effect of foeniculum vulgare on primary dysmenorrhea (pd). methods: in this study, we searched 19 databases (including medline/pubmed, scopus, isi web of science) for the effects of foeniculum vulgare on primary dysmenorrhea up to november 2016. the reference lists of the reviews and related articles were consulted to identify eligible articles. studies investigating combinations of fennel and other products, without a control group, addressing premenstrual syndrome (pms) and bleeding as the primary outcomes, and not being a randomized clinical trial (rct) were excluded. a meta-analysis was performed to obtain a pooled estimate of effectiveness. the methodological quality was assessed using the modified jadad scale. the registration number of this study is 95-01-65-11733. results: our search identified nine relevant articles for inclusion. the meta-analysis showed favorable effects of foeniculum vulgare on primary dysmenorrhea for fixed effect (n = 727, or = 0.573, 95% ci: 0.414 to 0.793, p = 0.001) and random effect (n = 727, or = 0.141, 95% ci: 0.027 to 0.742, p = 0.021). the analysis also revealed a remarked heterogeneity (q value = 198.318, p = 0.000, i² = 95.96, τ ² = 6.065). conclusions: we found that the fennel extract is effective for primary dysmenorrhea. however, due to the heterogeneity of various findings, we were unable to find the effective dosage and concentration of this herbal medicine.we recommend multi center clinical trials worldwide for evaluating the effectiveness of fennel in primary dysmenorrhea.