The authors will carry out the systematic review of studies focused on the father based on the Cochrane Handbook for Systematic Reviews following the recommendations of the Prisma method, also, we will evaluate the quality of each study through the Newcastle-Ottawa Scale (NOS) the version adapted for studies not randomized, and the Critical Appraisal Skills Programme (CASP)  to assess randomized, cohort, and cross-sectional studies. This review is registered in the International Prospective Register of Systematic Reviews PROSPERO (CRD42019142086). Bibliographic references will be administered in Mendeley. We will use for this protocol the steps of the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) . In the case that we identify multiple studies that in their method and results report homogeneity and allow for a meta-analysis, it will depend on the degree of heterogeneity of the data to choose whether to carry out a random-effects model or a fixed-effects model. To consider the degree of reliability of the studies, we will perform a chi-square (p> 0.05) or the confidence interval of the I2 statistical test .
The systematic review will include original articles, published in scientific journals, searches will be carried out from September 29, 2019, to September 29, 2020. Databases include APA PsycNet (American Psychological Association), BVS (Biblioteca Virtual em Saúde), Web of Science (Science and Social Science Citation Index), PubMed, Scopus, and The Cochrane Library (Cochrane Central Register of Controlled Trials - CENTRAL).
This systematic review design follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocols . For the keywords of the search, a vocabulary control was carried out on the MESH platform including some subtitles of the terminologies, to expand the search, some keywords of articles focused on the subject were used, we used a unique vocabulary for each database. Search strategies can be found in the supplementary file 1.
The PECOS (patient, exposition, comparison, outcome) approach was used to specify eligibility of studies. The population comprised of Fathers of premature babies in the ICU, The exposition comprised of Premature baby in the ICU. The control of Father-baby interaction. The outcome of Father´s experience.
The inclusion criteria will be studies published between 2010 and 2020; empirical studies in Portuguese / English / French / Spanish and full-text articles, in the event where access is restricted, we will request the full version to the authors via email. Dissertations, book chapters, reports, case studies, conference materials, reviews, and meta-analytic documents will be excluded from the main search. There also will be excluded studies in which the main objective is about the mother or that worked with teenage fathers. The research will be rerun during the completion of the work and further studies may be included. We will repeat the searches just before the final analyses, further studies may be retrieved for possible inclusion.
Underage Fathers of premature babies with gestational age less than 37 weeks, who are in the neonatal ICUs accompanying their hospitalized baby, clinical and non-clinical populations.
Types of outcome measures
We will consider as results any measure that includes the importance of the father in the neonatal unit; experiences of the father at that specific time accompanying his premature baby, as well as feelings and emotions (such as stress, distress, hope) during hospitalization in the neonatal ICU, also, the description of these experiences that can provide improvements for the development and health of the premature baby in the ICU follow-up, furthermore, how parents establish their attachment relationship with the premature newborn and how is their experience with the kangaroo care method.
Three researchers are involved in the study selection. Two reviewers will screen the articles, first by reading the titles, independently. The Mendeley Software will be used to check for duplicate references. The two reviewers will then screen remaining titles and abstracts for eligibility and will retrieve full-text of potentially relevant studies according to the inclusion criteria. In case of disagreement, a third reviewer will resolve through discussion the eligibility of certain studies. Upon completion of the research process, a manual search of eligible studies will be performed through the references of included articles to ensure the highest possible number of included studies.
Data Extraction Process
A standardized form will be used to extract the data from the studies. The following data will be extracted: article title; author(s); type of study (not randomized), journal title; publication year; recruitment method; participants (fathers); the context of study realization; sample characteristics (e.g. presence of fathers); study objective; to talk about the experience or perception of the father during the stay of the premature infant in the neonatal ICU.
Two reviewers will retrieve the data in a standard and independent manner. A third author will resolve potential discrepancies and disagreements. We will evaluate the studies ‘quality with the Newcastle-Ottawa Scale (NOS), a quality scale with three categories: selection, comparability, and outcome  see more in appendix 1. We will also use CASP, which is a qualification list with 10 criteria, that assesses randomized, cohort, and cross-sectional studies and categorizes them as high (8 to 10), medium (5 to 7), or low quality (4 or fewer) see more in appendix 2 .
The synthesis will be realized using the final data extraction. A narrative synthesis with categories of analysis will be created, focusing on the review questions, mainly associated with the objective reached about how is the father's experience in the neonatal ICU with his preterm baby.
Patient and Public Involvement:
This is a systematic review, which means that we won't work with patients or the public.