This study is a systematic review and meta-analysis based on the findings of previous studies conducted on the prevalence of insomnia in the third trimester of pregnancy, including articles published in domestic and foreign journals obtained by searching at Scopus, Embase, Science Direct, Web of Science (WoS), SID, Mag Iran, Medline (PubMed), IranDoc and Google Scholar until December 2020.
The search process was performed in Persian and English databases using keywords, including disorders of initiating and maintaining sleep, insomnia, pregnancy and third trimester. The AND/OR operators were also used in this study to provide more comprehensive access to all articles. Therefore, the AND/OR operator was used to check the disorder’s common names by matching words in the MeSH browser.
PubMed search strategy: (((((Sleep [Title/Abstract]) OR Sleep Habits [Title/Abstract]) AND Insomnia [Title/Abstract]) OR Sleep Initiation and Maintenance Disorders OR Sleep Habits [Title/Abstract]) OR Chronic Insomnia [Title/Abstract]) OR Disorders of Initiating and Maintaining Sleep [Title/Abstract]) OR DIMS [Title/Abstract]) OR Nonorganic Insomnia [Title/Abstract]) OR Primary Insomnia [Title/Abstract]) OR Psychophysiological Insomnia [Title/Abstract]) OR Sleeplessness [Title/Abstract]) OR Insomnia Disorder [Title/Abstract]) AND Pregnancy [Title/Abstract]) OR Pseudopregnancy [Title/Abstract]) OR Pregnant Women [Title/Abstract]) AND Third Trimester of Pregnancy [Title/Abstract]) OR Pregnancy Trimester, Third [Title/Abstract]) OR Last Trimester [Title/Abstract]))))).
Inclusion and exclusion criteria
The studies’ inclusion criteria include 1- Cross-sectional studies, 2- population-based study, 3-studies that have examined insomnia in the third trimester of pregnancy, 4- analytical descriptive studies (non-interventional studies), and 5- studies in the English language.
Exclusion criteria of the studies include 1- case-control studies, 2- case report, 3- interventional studies, 4-letter to the editor, 5- studies with no full-text availability 6- studies not related to the subject, 7- studies without sufficient data, 8- repetition of studies, and 9- review studies.
Criteria for selection and evaluation of articles and quality assessment
In order to maximize the comprehensiveness of the search, the list of sources used in all related articles found in the above search was manually reviewed. Initially, studies that were repeated in various databases searched were removed from this study. Then, a list of all the remaining articles’ titles was prepared to get qualified articles by evaluating the articles in this list.
In the first stage, duplicate publication and multiple publications from the same population were removed using EndNore citation management software (version X7, for Windows, Thomson Reuters).
The title and abstract of the remaining articles were carefully studied in the next step, and unrelated articles were removed according to the inclusion and exclusion criteria. In the third stage, i.e. the evaluation of the competence of the studies, the full text of the possible related articles remaining from the screening stage was examined based on the inclusion and exclusion criteria, and unrelated studies were also removed in this stage. To prevent bias, all sources of resource review and data extraction were performed by two researchers independently. If the articles were not included, the reason for deleting them was mentioned. In cases where there was a disagreement between two researchers, a third person would review the article.
In the final stage, the quality of the studies was examined, and the STROBE checklist was used to review the studies. This checklist contains 22 sections, 18 of which are general and practical for all observational studies, including cohort, case study, and cross-sectional ones. Accordingly, the maximum quality score of 32 was considered, and papers with a score of less than 14 were considered to have low quality, and they were thus excluded from the study.
In each study, the prevalence of insomnia in the third trimester of pregnancy was obtained. The heterogeneity of the studies was evaluated using the I2 test. Generally, heterogeneity is classified into three categories: heterogeneity> 25% (low heterogeneity), 25–75% (average heterogeneity), and 75% > higher (high heterogeneity). In order to review the analysis of the studies, it was decided based on the results of heterogeneity. If the heterogeneity was less than 20, the method of fixed effects was used, and if it was higher, the method of random effects was used. Egger’s test was used to statistically analyze the publication bias and the significance level of 0.05. The probability of publication bias in results was shown using the funnel plot. Also, the possible effects of heterogeneity in the studied studies were investigated using meta-regression analysis. The data were analyzed using the Comprehensive Meta-Analysis (Biostat, Englewood, NJ, USA Version 3).