Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)  were used to prepare and present this systematic review and meta-analysis (Supplementary File 1).
We used the PEO technique (Population, Exposure of interest, Outcome) to establish the inclusion and exclusion criteria.
Population Teenagers (10 to 19 years old).
Exhibition of interest Earn pocket money.
Outcome of interest Good management of menstrual hygiene.
Study designs All observational study designs reporting the association between earning pocket money and menstrual hygiene were considered. In addition, studies that presented an adjusted odds ratio (OR) to assess the association between earning pocket money and menstrual hygiene management were considered for inclusion in the meta- to analyse.
Study framework Only studies conducted in Ethiopia.
Post status Both published and unpublished studies were considered.
Study period There were no restrictions on the publication date.
Language Articles published in English were taken into account.
Year of publication All posts reported up to September 15, 2021 have been considered.
Study design: Systematic reviews, commentaries, letters to editors, short communications and qualitative studies were excluded. We also excluded articles that were not fully consulted.
Sources of information
The following databases were searched extensively with no time limit. PubMed/MEDLINE, Science Direct, Google Scholar, Hinari, ProQuest, Directory of Open Access Journals, POPLINE and Cochrane Library from inception to September 15, 2021.
The following key search terms and medical subject titles [MeSH] have been used (“teenage girl [MeSH Terms]OR Teenagers [Text Word]OR adolescence, OR puberty, OR peers, OR school”) AND (“Menstruation [MesH]OR menstrual, OR periods” AND “Hygiene [MesH]OR hygiene, OR hygienically, OR sanitation, OR sanitary, OR feminine ”Hygiene products” [MesH]OR ”Menstrual hygiene products” [MesH]”) AND (“Ethiopia”) separately or in combination with the Boolean operator terms “AND” and “OR” (Supplementary File 2). The electronic database search was supplemented by gray literature searches via Google Scholar and Google Search. Selected research centers, including the Addis Ababa Digital Library, were searched for gray literature in the area of our systematic review and meta-analysis. A secondary research method known as “footnote chasing” was used to identify relevant articles.
This systematic review and meta-analysis includes all articles published up to September 15, 2021, and the search was performed between August 15 and September 15, 2021.
Study selection process
Two investigators (BS and DA) independently screened and identified eligible articles by title, abstract, and full text against predefined inclusion and exclusion criteria. Both authors (BS and DA) compiled the selected articles and disagreements between them were resolved by discussion. In this review, all searched articles were exported to EndNote software version X8, and subsequently duplicate articles were removed. Selection of retrieved article titles, abstracts, and full-text quality was performed independently by two review authors (BS and DA) based on the eligibility criteria.
Data collection process
Microsoft Excel was used to extract the data. Two authors (BS and DA) retrieved all necessary data independently using a predefined data extraction form. Any disagreements that arose during the data abstraction process were resolved through discussion. Senior author, year of publication, study design, study area, sample size, response rate, proportion of good menstrual hygiene management, and OR adjusted for confounders were all included in the data extraction format. EndNote version 8 reference management software was used to collect search results and remove duplicate articles.
Assessing risk of bias of studies
The Joanna Briggs Institute (JBI) quality assessment method was used to assess the quality of included studies. . The quality of included studies was assessed independently by two reviewers (BS and DA). The assessment tool has nine parameters. The non-satisfaction of one of the parameters resulted in a 1, otherwise a 0. We agreed to assign a 1 to an item when the information provided was insufficient to make a decision (non-satisfaction of a precise item or little light). Risk of bias was categorized as low (total score of 0 to 2), moderate (total score of 3 or 4) or high (total score of 5 or more) .
Summary of results
For statistical analysis, the extracted data were imported into STATA version 14 software. First, we extracted the adjusted ORs of all included studies. The adjusted odds ratios (AORs) were then aggregated using the generic inverse variance method, which involved converting the adjusted odds ratio to a logarithmic scale and then calculating the standard error [SE] based on 95% confidence intervals. The Cochran Q (standard X2) test and Haggin I2 statistics were used to assess the presence and degree of heterogeneity among the included studies. The tests indicate the presence of moderate heterogeneity among the included studies [I2 = 66.7%, p-value = 0.006]. Thus, ORs were pooled using random-effect meta-analysis techniques using the DerSimonian and Laird method, which accounts for variation between studies . Grouped ORs with their 95% confidence intervals [CI] were presented using a forest chart.
In this meta-analysis, possible publication bias was visualized using funnel plots. A large symmetrical inverted funnel resembled the absence of publication bias. Additionally, the likelihood of publication bias was tested using Egger’s weighted regression test.
Subgroup analysis and meta-regression
We performed subgroup analysis based on geographic regions, sampling methods, data collection method, sample size, year of publication, and type of adjusted confounders in a primary study. Other statistical analyzes such as univariate meta-regression were also performed to identify possible sources of heterogeneity.
A sensitivity analysis using a random-effects model was performed to assess the influence of a single study on the overall estimate of the pooled odds ratio.
Good management of menstrual hygiene
Teenagers use clean menstrual management equipment to absorb or collect blood which can be changed privately as often as needed for the duration of the menstruation period, using soap and water to wash the body if necessary , and having access to facilities to dispose of used menstrual management materials.
Earn pocket money
In this article, the term “pocket money” refers to any amount of money received by adolescent girls from their family or relatives to buy menstrual hygiene products.