Table 11 COREQ Checklist: Methods and reporting according to COREQ statement

1. Interviewer

JLG, MF, and MJA conducted the interviews.

2. Credentials

Three psychologists conducted the interviews:

JLG, MSc in Psychology

MF, PhD in Psychology

MJA, MSc in Psychology

3. Occupation

JLG was a PhD student at the University of Porto.

MF was an Associate Professor at School of Education, Lisbon Polytechnic Institute and a Researcher at the Centre for Psychology, University of Porto.

MJA was a researcher at School of Education, Lisbon Polytechnic Institute.

JLG was awarded with the cited doctoral grant from the Portuguese Foundation for Science and Technology (SFRH/BD/90853/2012).

MF was the PI of the project funded by the cited grant from the Portuguese Foundation for Science and Technology/FEDER (PTDC/MHC-PED/1424/2014).

MJA received salary support from the cited grant from the Portuguese Foundation for Science and Technology/FEDER (PTDC/MHC-PED/1424/2014).

4. Gender

All interviewers were female.

5. Experience and training

All interviewers had prior interviewing experience. Qualitative research training in interview conduction and analysis was provided to JLG, MF and MJA within the scope of their academic training in Psychology.

Relationship with participants

6. Relationship established

A prior relationship between the interviewer and participants did not exist (with the exception of the brief initial contact at the time of recruitment, when mothers were invited to participate in the study).

7. Participant knowledge of the interviewer

Prior to any data collection, we provided all potential participants with an overview of the study prior to signing of the informed consent. The interviewer provided a brief introduction prior to beginning an interview.

8. Interviewer characteristics

No specific bias or assumptions to declare for any of the interviewers.

All interviewers have been working on the field of clinical, neonatal and developmental psychology, with relevant published work concerning mother-infant relationship in the context of distinct infants’ at-birth-risk conditions, with a particular focus on the preterm birth within the scope of their research interests.

9. Methodological orientation and Theory

The maternal interview followed the procedures of a previously established protocol [50], to collect mothers’ pre- and perinatal experiences in the first 72 h after infants’ birth.

Following the guidelines used in the previous study, we used content analysis, combining both grounded-theory and a hypothetical-deductive method which resulted in 5 themes and 7 subthemes.

Using grounded theory to inductively derive additional themes that characterized the transcripts allowed to further describe our findings.

10. Sampling

Purposive sampling.

11. Method of approach

Participants were identified by two female research assistants who contacted personally, face-to-face, eligible mothers after delivery and explained the study’s purpose and procedures.

12. Sample size

Although the total sample size in the study is large, there are three sub-groups, allowing in-depth analysis of all viewpoints.

The three groups of mothers were recruited, with the aim of exploring their maternal pre- and perinatal experiences in depth, in the context of distinct infants’ at-birth-risk conditions.

Content analysis does not preclude the use of large numbers and, as with all qualitative research, does not claim generalisations [98].

According to Bengtsson [99], in qualitative studies, normally, data are based on 1 to 30 participants. However, the author stresses that sample size should be determined on the basis of informational needs so that it is possible to organize and elicit meaning from the data collected and to draw realistic conclusions from it, and ultimately, to answer to the research question at study with sufficient confidence.

In our study, we expected a large diversity of responses and speeches (considering the large diversity of mothers’ backgrounds and health conditions associated with prematurity) resulting in several indicators in each unit of analysis.

Therefore, we decided to enlarge the sample to 50 participants to have enough representative and clarifying information for each subtheme and indicator in each group.

13. Non-participation

No mother withdrew from participating in our study after signing the informed consent.

14. Setting of data collection

At each of the three participating hospitals, we asked for a quiet silent room or office available in the maternity or nearby where the interview was conducted.

15. Presence of non-participants

Our protocol did not allow non-participants. Any non-participants were immediately asked to leave if they entered the room where an interview took place.

16. Description of sample

Our protocol allowed for collection of demographics, family, socio-economic characteristics, as well as medical and clinical information of the infant, mother and their families.

17. Interview guide

This was pilot tested in a previous study [50]. The interview protocol is available as additional file in Appendix 2.

18. Repeat interviews

No, our protocol was defined so that the interview should be conducted only one time, at the first 72 h postpartum, although flexibility was given for mothers to choose the best and most appropriate time within this temporal window. It was not our aim to conduct the same interview with the same participant more than one time.

19. Audio/visual recording

Digital audio recordings were made and transcribed verbatim.

20. Field notes

Field notes were not taken since the digital recordings were rapidly reviewed upon the return of the study team to the research center at the University.

21. Duration

The individual one-on-one and face-to-face interviews lasted approximately 1 h.

22. Data saturation

Lincoln and Guba’s [100] four criteria for trustworthiness (credibility, dependability, confirmability and transferability) were used to ensure rigor in the qualitative process. Notes were taken while data coding to capture the participants’ voices and the meaning behind their words and to assist in eliminating potential bias or misinterpretation. Data analysis began with the first interview and continued through formulation of the five main themes, the various subthemes and into reporting of the findings. In qualitative research, the data lend itself to interpretation by the researcher. The themes extrapolated from the data were supported with rich data and use of participant’s own words added to the authenticity. Data saturation was reached early in the process; however, the researcher continued to read and reread each transcript with attention to detail. The lived experiences of the participants were revealed and not subject to bias of the researcher.

23. Transcripts returned

We did not return transcripts to participants for comment and/or correction. However, (1) participants were provided with information related to dissemination of the research findings and given time to ask questions related to the basis for the research and (2) a group of 10 parents (both mothers and fathers) in the preterm group were invited to take part in a videotaped focus group to discuss and reflect about the study findings.

Regarding ethical considerations, the transcripts had personal identifiers that were removed to protect the participants in the event of a security breach. After reviewing the transcripts for errors and inserting field notes, the researcher deleted all audio recordings.

24. Number of data coders

All the seven authors participated in the coding process.

25. Description of the coding tree

The coding tree used for initial assignment into the 5 major themes, that had already been used in a previous study [50], is described in the methods.

26. Derivation of themes

Major themes were derived in advance; minor or subthemes were derived from the data inductively.

27. Software

No software was used.

28. Participant checking

To learn more about the participants’ perspectives, we invited a group of 10 parents (both mothers and fathers) in the preterm group to take part in a videotaped focus group to discuss and reflect about the study findings. The parents confirmed that the identified themes and subthemes reflected their experience, demonstrating an identification with the study results and stressing the need for more effective support responses in the hospital maternity and after discharge.

29. Quotations presented

See results section (participants quotations were presented to illustrate the findings and each quotation is identified through the participant number).

30. Data and findings consistent

Questions 30–32 of COREQ address the evaluation of the findings of a qualitative study and are intended for readers of qualitative research. They are included here for completeness. We have attempted to present our findings in this work clearly in a manner that was consistent with the data collected.

31. Clarity of major themes

Major themes were clearly presented and discussed in the results and discussion sections.

32. Clarity of minor themes

Minor themes were clearly presented and discussed in the results and discussion sections.