Foster care can be seen as a temporary measure to protect and promote the development, well-being, and education of children in a stable and safe family environment (i.e., the foster family) while the birth family works to meet the necessary conditions for the child’s return home (Moro et al., 2007). Although justified, this approach frequently involves removing the child from their natural environment, which includes their family, friends, and school. Additionally, it usually requires placing the child in a completely new environment with new caretakers, and the child often is not aware of or does not understand the circumstances prior to the placement. The reactions of both the child and the birth parents to the child’s removal from the home can range from negative to positive, and adapting to this new reality is largely dependent on the communication between the families (Tribuna & Relvas, 2002). According to Bertão et al. (2015), establishing and maintaining a good relationship between birth and foster parents has several benefits, such as managing expectations, creating an educational project in which everyone is involved, sharing education methods and strategies, and allowing children to express affection for their foster parents without fear of being disloyal to their birth parents. Additionally, a positive relationship facilitates children’s social integration and sense of security in their new environment, reducing risk behaviors and escapes from the foster home, particularly in the case of older children/adolescents (Andersson 2009; Holtan 2008; Linares et al. 2006a, b a). Sen and Broadhurst (2011) suggest that if the relationship between birth and foster parents is unplanned, of poor quality, or lacking any type of professional support, it can be harmful to the child, especially if there has been a history of mistreatment. The legal grounds and associated concerns leading to the child’s removal should not be overlooked, as they may significantly influence the relational dynamics between birth and foster parents (Corser & Furnell, 1992).

Thus, the research points to the importance of the relationship between birth and foster parents, even when children will be adopted and will not be reunified with their birth family (Collings et al., 2020). On the one hand, if the contact between the birth and foster parents is positive, it can help the child to mourn the “old” family, to accept their life situation, to strengthen ties with the “new” family, and to maintain good relations with everyone. On the other hand, if that contact is not positive, it can weaken children’s sense of security and the stability of their placement in the “new” family, leading to feelings of confusion, distrust, abandonment, and distress (Boyle, 2017).

It has been suggested that providing information, support, resources, and tools that can help these families to connect is crucial (Carvalho et al., 2019; Delgado et al., 2014; Sen & McCormack, 2011). However, researchers have not yet documented in depth how birth and foster parents relate with each other, what contributes to the quality of this relationship, or their perspectives on the factors that influence the relationship’s beginning, maintenance, or ending (Chateauneuf et al., 2018; Järvinen & Luckow, 2020). Previous systematic literature reviews on foster care have covered topics related, for example, to the relationship between birth parents and their children before, during, and after the placement (e.g., Havlicek, 2021; Poitras et al., 2022); the adjustment of the child to the placement (e.g., Saarnik, 2021); the intention to become and to continue as foster parents (e.g., Gouveia et al., 2021); the behavioral and emotional issues and needs of foster children (e.g., Engler et al., 2020; Hegar & Rosenthal, 2009), interventions and training for foster parents (e.g., Kaasbøll et al., 2019; Kinsey & Schlösser, 2012), and attachment between the child and the foster family (e.g., West et al., 2020). To our knowledge, no systematic review has focused specifically on the relationship between birth and foster parents. Therefore, the purpose of this systematic literature review is to examine the empirical research addressing our main research question: What factors influence the relationship between birth and foster parents? In addition, this review may provide a foundation for future research while also expanding the knowledge required to develop and disseminate high-quality interventions and training programs to promote positive relationship patterns between birth and foster parents.

Method

Data Collection Strategies

To develop a strategy on data collection, the research question was formulated in accordance with the SPIDER method (Sample, Phenomenon of Interest, Design, Evaluation and Research Design; Cooke et al., 2012): (a) sample—birth parents of children placed in foster families and foster parents; (b) phenomenon of interest—foster care; (c) design—all designs and empirical methods except literature reviews and single case studies; (d) evaluation—specific information about the relationship between birth and foster parents (e.g., information on frequency, context, content, and quality of the relationship); and (e) research design—qualitative, quantitative, or mixed methods.

The search was performed in January 2023 in the online databases Web of Science and Scopus, using the following combination of terms: (relation* OR contact* OR communicati* OR interacti* OR connecti* OR collaborati* OR cooperati* OR conflict* OR difficult* OR negotiat*) AND (“Biological famil*” OR “birth famil*” OR “origin famil*” OR “biological parent*” OR “birth parent*” OR “origin parent*” OR “birth mother*” OR “natural parent*”) AND (“Foster famil*” OR “foster parent*” OR “foster care*”). The specific restrictions applied were the articles had to be published in peer-reviewed academic journals and written in English, Portuguese, or Spanish. No restrictions were placed on the publication date. Duplicate studies were verified and removed. No protocol registration was performed. Various terms are used in the literature to refer to the parents of foster children; the authors chose to use the terms birth parents and foster parents throughout this article.

Criteria for Inclusion and Exclusion of Studies

The inclusion criteria were (1) qualitative, quantitative, or mixed methods studies; (2) studies that explored (exclusively or not) the relationship between birth and foster parents or their perceptions of each other; (3) studies involving birth and/or foster parents; (4) studies involving non-kin foster parents or mixed (kin and non-kin in the same study); (5) studies that anticipated family reunification or did not specify the outcome; and (6) studies that examined the relationship between birth and foster parents. The exclusion criteria were (1) single case studies, literature reviews, or studies that assessed the results of therapeutic interventions or psychoeducational programs; (2) studies that explored the relationships between foster parents and children, foster parents and case-workers, birth parents and children, birth parents and case workers, children and case workers, children’s perceptions, case workers’ perceptions, or the perceptions of others not associated with these relationships; (3) studies restricted to foster children, to case workers, or to family members who were not the parents; (4) studies of kin foster parents (exclusively); (5) studies that focused on adoption, residential foster care, or youth autonomy; and (6) studies that did not specifically explore the relationship between birth and foster parents.

Article Selection Process and Data Extraction

We conducted the initial data collection from databases using Mendeley Desktop and carried out the entire review process manually. Each of us served as a coder, with the support of a flow diagram describing the number of studies identified using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA; Page et al., 2021). Figure 1 shows the flow diagram for the study selection process.

The search initially retrieved 904 articles, which were imported into Mendeley. We did not perform a hand search for additional articles. After removing duplicates, the coders began the process of rejecting or retaining articles. This analysis was carried out independently; the first author reviewed all articles, and the second and third authors reviewed one half each. Thus, two coders reviewed every article to ensure that the inclusion criteria were strictly attended to and to minimize the risk of subjectivity bias (as recommended by Haddaway et al., 2015). We retained a total of 571 articles by considering only their titles and abstracts. At this stage, we did not disagree regarding which articles to keep and to reject. After the initial screening, we excluded 530 articles and selected 41 for full-text analysis. The inter-judge agreement was 90% once we agreed on the inclusion/exclusion of 37 articles and disagreed on the other four. Our disagreements and uncertainties were resolved by a discussion among the three coders about the specificities of the articles and the application of the inclusion/exclusion criteria. As a result, 19 of the articles were removed and 22 were included in this review. We used an extraction sheet to register relevant data, which included the author(s), year of publication, country in which the study was conducted, title, research purpose, methods used to conduct the study, participants, and main findings (Table 1). Data analysis followed the phases of thematic synthesis proposed by Thomas and Harden (2008). Initially, the results sections of the studies were analyzed using line-by-line coding to produce inductive codes. These codes were then compared to identify similarities and differences, from which descriptive themes were constructed. In the final phase, the descriptive themes were interpreted to generate analytical themes that addressed the research question.

Results

Characteristics of the Studies

Out of the 22 articles included in the final review (Table 1), five used quantitative methods (e.g., scales, questionnaires, surveys), 16 employed qualitative methods (e.g., interviews, focus groups, conversation analysis), and one used a mixed approach (multiple case studies). Interviews was the most used data collection method among the qualitative approaches (12 articles). The articles were published between the years 1992 and 2022, with the majority published after 2009. A total of 2,736 participants were involved in the studies, and sample sizes ranged from 63 to 950 participants in the quantitative studies, 10 to 141 in the qualitative studies, and 58 in the mixed methods study.

Participants’ characteristics varied. The studies included only birth parents (n = 4); only foster parents (n = 10); both birth and foster parents (n = 4); foster parents and social workers (n = 1); birth and foster parents and social workers (n = 2); and foster parents, social workers, and children (n = 1). Thirteen publications that focused on birth and foster parents specified the number of mothers, fathers, and/or couples (both mother and father) that took part in the research. The remaining nine articles did not mention this number or did not identify the participants’ sociodemographic characteristics. The articles that provided these demographics had more couples (n = 189) than mothers alone (n = 185) or fathers alone (n = 52) as participants, resulting in more females (n = 374) than males (n = 241) participating in the studies.

Thirteen studies were carried out in Europe (mostly in northern countries), four in North America, one in Asia, three in Australia, and one was intercontinental (both America and Europe). All articles were written in English.

Emerging Themes

Thematic synthesis revealed domains influencing the relationship between birth and foster parents, leading to four themes: (1) intentions and efforts to cooperate, (2) quality of contact and communication, (3) role expectations, and (4) perceptions of professional support.

Intentions and Efforts to Cooperate

Seven of the reviewed studies examined relationships in terms of birth and foster parents’ intentions and efforts to cooperate and establish positive and healthy bonds with one another. These intentions and efforts seem to be primarily influenced by each parent’s perceptions of “the best interest of the child” (Bengtsson & Karmsteen, 2020; Järvinen & Luckow, 2020; Jones et al., 2016), the characteristics of the birth and foster parents (Basiaga et al., 2018; Erera, 1997; Riggs, 2014), and the circumstances surrounding the child’s removal (Corser & Furnell, 1992).

Regarding perceptions of the best interest of the child, Bengtsson and Karmsteen (2020) examined birth parents’ experiences of collaborating with foster parents and found that although birth parents wanted their love for their child and their parenthood to be acknowledged, most did not cooperate with the foster parents at all (n = 8); the rest consistently showed little cooperation (n = 4) or only cooperated sometimes (n = 6). Järvinen and Luckow (2020) found that both birth and foster parents perceived themselves in a struggle around what would be good or bad for the child. The authors suggested that the birth parents (n = 15) felt they wanted the foster parents to take good care of their children, but they also felt threatened in their parenting role because they were afraid that the foster parents would take their place and that the children would prefer the foster parents. The same authors also stated that the foster parents (n = 16) wanted to maintain a close relationship between the children and their birth parents but witnessed that the children’s emotions and behaviors were negatively affected by the birth parents’ problems and inconsistencies. Jones et al. (2016) found that although the relationship with birth parents could be a challenge for foster parents, they still made an effort to respect, be involved with, and support birth families because they knew how important it was in helping children successfully adapt to placement.

On the perceptions of birth and foster parents, Basiaga et al. (2018) found that, despite legal obligations regarding contact during foster care, the temporary nature of foster care, and the child’s expected return to their family, 65.5% of foster parents had a negative attitude towards birth parents and the reunification process. This resulted in poor or absent intentions and efforts to communicate with birth parents. Foster parents argued that this negative attitude came from their observation of the birth parents’ lack of parenting skills as well as the absence of opportunities to teach them these skills. Erera (1997) concluded that most foster parents had no relationship with birth parents mainly because they had minimal or no contact at all with them (they were geographically distant from each other). In addition, foster parents felt it was unnecessary, unproductive, or inappropriate to interact with the birth parents. Riggs (2014) found that many foster parents disagreed with the intimate presence of birth parents in their lives and wished to distance themselves. A small minority stated that they were able to maintain relationships with birth parents regardless of their opinions about the birth parents’ life and parenting skills.

Regarding the causes of children’s removal from their home due to abuse, Corser and Furnell (1992) found that, for foster parents, the relationship with birth parents was more acceptable when the abuse was negligence, not physical and/or sexual abuse, with the latter type being the least acceptable.

Quality of Contact and Communication

Six studies described particular characteristics of contact and communication between birth and foster parents that indicate whether the relationships were of higher or lower quality. These characteristics were the parents’ understanding and acceptance of foster care (Berrick & Skivenes, 2012; Chateauneuf et al., 2018; Hedin, 2015), behavioral and socio-emotional skills (Collings & Wright, 2022; Wilson et al., 2000), and use and frequency of various forms of communication (Sliedrecht et al., 2022).

Regarding the foster parents’ understanding and acceptance of foster care, Berrick and Skivenes (2012) suggested that, for most foster parents, the relationship with birth parents were of higher quality when the child’s integration, empathy, respect, and the value of the connection between the child, birth parents, and foster parents were prioritized. In their study, Chateauneuf et al. (2018) found that 15 out of 29 foster parents who commented on the quality of the relationship had a positive relationship with the birth parents, demonstrating signs of respect, confidence, and recognition of each person’s role. Five foster parents had a mediocre relationship, while three had a difficult relationship, characterized by bad interactions with one or both parents, tension, disappointment, extreme competition, and a lack of confidence in each other. The remaining six foster parents had little or no contact at all because the birth parents had stopped making contact or only visited the child rarely. Therefore, according to the authors, birth parents’ understanding and acceptance of their child’s placement in foster care is a key element in developing a positive relationship. In Hedin’s (2015) study, birth and foster parents reported that getting to know each other prior to the child’s placement led to a good relationship, allowing the development of positive attitudes and expectations towards each other and facilitating trust, as well as better cooperation in small and large events of the child’s daily life.

Considering behavioral and socio-emotional skills, Collings and Wright (2022) found that the dyads of birth and foster mother that displayed more emotional competence (e.g., empathy and emotional intelligence, and care and nurturing), relationship skills (e.g., modeling respect and conflict resolution), positive beliefs about contact (e.g., performing parenting and agency supervision), and understanding of power issues (e.g., resolving legal ambiguity, resolving identity ambiguity, and addressing boundary issues) reported better relationships. In contrast, a quarter of the foster parents in Wilson et al.’s (2000) study reported difficult relationships with birth parents as a result of aggressive or violent behavior on the birth parents’ side (such as threatening or making false allegations against the foster family). This sort of poor relationship usually lead to disruptive behaviors in the children, making the placement more difficult or even impossible to maintain.

Regarding the use and frequency of various forms of communication, Sliedrecht et al. (2022) found that regular communication between the two parties via phone calls, text messages, or images was appreciated. This allowed birth and foster parents to share news and responsibilities related to the child.

Role Expectations

In four studies, birth and foster parents’ interpretations of what was expected (and not expected) regarding the foster child (i.e., the role each parent would play in the child’s life and their individual responsibilities) appeared to be an important factor in shaping and maintaining their relationship (Höjer, 2009; Pinto & Luke, 2022; Salem & Wilde, 2022; Weitz & Karlsson, 2021). In a study conducted by Höjer (2009), most birth parents admitted feeling inferior to foster parents in their parenting skills after they failed to provide adequate care for their child, which led to the placement. These feelings, in turn, created an asymmetrical pattern in the relationship between birth and foster parents because the more efforts the birth parents made to improve their life conditions and parenting skills, the worse their relationship with the foster parents became. They perceived that the foster parents expected them to continue in the inferior role, remaining a bad parent or at least not as informed or capable as the foster parent. This hierarchy seemed to grant some stability in their interactions, yet it was incompatible with birth parents’ improved skills and the initiation of the reunification process. Therefore, these birth parents emphasized the need for foster parents to be well informed about their fostering tasks (what to do and not to do) as well as to interact positively and cooperate with birth families. They added some prerequisites for good cooperation in performing these tasks, such as openness, clarity, respect, and goodwill.

Comparing the results from samples in two countries—England and Portugal—and considering these countries’ cultural, historical, and legislative differences, Pinto and Luke (2022) found that some Portuguese foster parents in their study acted as if the children were their own, placing a strong emphasis on the parenting role. Also, these foster parents tended to neglect the birth parents’ role and even question social services and the court’s decisions about contact, causing tensions with birth parents. The authors found that English foster parents, in contrast, typically performed a broader and more structured role, combining the parenting role with other tasks needed to fulfill the success of the temporary measure. Because of this, they tended to see the birth parents as a source of support.

Salem and Wilde (2022) identified three major factors that can shape the way birth parents view and engage their new role once the child is placed in foster care: sudden placement, the foster care process, and feeling like a parent. The birth parents who participated in their study revealed a new understanding of their role as parents once there was a significant change in their family life as well as in their daily routines and responsibilities. Finding a different way of parenting (but still being positive and proactive in their children’s lives) was crucial for birth parents to be able to establish good relationships with foster parents.

Focusing on the tension related to competitiveness between birth and foster parents, Weitz and Karlsson (2021) identified three major narratives in their sample of 16 birth parents, stating that the birth mother perceived herself as an (a) irreplaceable, (b) misunderstood, or (c) remote mother and perceived the foster mother merely as a professional doing a job. The authors stated that this type of moral discourse on motherhood was an attempt by the birth parents to make sense of foster care and shared parenthood, although it seemed to limit their cooperation.

Perceptions of Professional Support

Five studies examined birth and/or foster parents’ perceptions of the availability of social services to guide and assist them during the fostering experience. Perceptions of the presence or absence of guidance and validation seemed to influence how birth and foster parents evaluated the importance of their relationship, their behavior within these interactions, and even the relationship’s success or failure (Broady et al., 2010; Fuentes et al., 2019; Gilligan, 1996; Sanchirico & Jablonka, 2000; Spielfogel & Leathers, 2022).

Broady et al. (2010) identified five domains of foster parents’ experience (birth family, motivation, agency influences, relationship impacts, and attachment) that revealed difficulties with training procedures and the absence of ongoing support from social services. These struggles were found to both influence and be influenced by the relationship between birth and foster parents and were seen as determining foster parents’ decision to provide care in the future, as well as the quality of the care they provided.

In the Fuentes et al. (2019) study, participants identified a number of difficulties between birth and foster parents, perceiving the difficulties as resulting from poor competency training and support given by social workers. These difficulties involved mistrust, fear, conflicts of loyalty, poor communication, anxiety, lack of safety in relation to some of the birth parents’ behaviors, negative views of each other, absence of information, complaints, false expectations, and distress in children.

Although most foster parents in Gilligan’s (1996) study felt that the social workers prepared them well for foster care, a significant number questioned the importance of contact with birth parents, revealing a need for awareness of the value of birth parents as well as training to facilitate better relationships and management of behaviors. Sanchirico and Jablonka (2000) found that the training and support provided to foster parents were directly related to the foster parents’ relationship with the birth parents. More specifically, foster parents who had received training and support carried out more visitation and non-visitation activities (e.g., arranging visits, encouraging phone calls, and involving the birth family in celebrations and decision-making). Foster parents who received only training or only support performed fewer activities, whereas those who did not receive either training or support performed the fewest activities.

In Spielfogel and Leathers’ (2022) study, caseworkers often left the decision about whether or how to communicate with birth parents up to the foster parents. This meant the foster parents had no expectations management, or guidelines for collaboration with birth parents. The birth and foster parents were not properly prepared to relate in a positive and well-adjusted way, which had various outcomes—some parents collaborated, some refused to collaborate, and others were in conflict. The outcome depended on the birth and foster parents’ initiative, willingness, experience, and attitude.

Discussion

The aim of this study was to present a systematic review of the empirical literature on the relationships between birth and foster parents. A total of 22 articles were identified and summarized regarding the study’s sample, context, and main findings, allowing us to identify four major domains that seem to shape these interactions. As far as we know, this is the first systematic literature review of contributing factors to the establishment and maintenance of this relationship. The findings suggest that relationships between birth and foster parents are shaped by each party’s intentions and efforts to cooperate, the quality of contact and communication, the expected and unexpected roles played by each party, and the parents’ perceptions of professional support.

Regarding birth and foster parents’ intentions and efforts to cooperate, seven articles (i.e., Basiaga et al., 2018; Bengtsson & Karmsteen, 2020; Corser & Furnell, 1992; Erera, 1997; Järvinen & Luckow, 2020; Jones et al., 2016; Riggs, 2014) found that the initiation of the relationships relies on the willingness of the birth and foster parents to talk, to visit, and to help each other. Three of these publications pointed out the ambiguity in determining what is the best for the child—the attitudes, actions, and outcomes that would help the child to have a healthy and secure development. Given this subjectivity based on each parent’s reality, birth and foster parents’ opinions and attitudes towards themselves or each other may sometimes be contradictory. These findings suggest that when birth and foster parents disagree on this issue, it is harder to achieve cooperation and, consequently, to have a good relationship. Three other studies we reviewed emphasized how birth and foster parents evaluate each other’s personal characteristics in terms of parenting skills and life history. Even though contact between the parties is sometimes a legal requirement, when there are negative beliefs about the other party’s personal competence, parenting skills, and overall life experience, intentions and efforts usually are few or even nonexistent. One article focused on the differences in responses based on the reasons for child removal (physical abuse, neglect, or sexual abuse).

These studies suggest that foster parents tend to form critical judgments when they have access to the history of the child and their birth family. These judgments are based on their own perceptions of the child’s experience. The more serious they view the situation, the fewer their intentions and efforts to cooperate with the birth parents. This issue of intentions and efforts might arise early on in foster care systems since, according to Skivenes (2010), there has been frequent criticism of legal child protection services because of their often arbitrary and subjective decisions. Furthermore, this aligns with the findings from Ankersmit’s (2016) qualitative study of good collaborations between birth and foster parents. Specifically, developing trust and acceptance of the foster care system and of every person involved in it and their capabilities is important, as is the need for birth and foster parents to have sufficient knowledge about each other and to agree on the plan for the foster child.

On the quality of contact and communication, six articles (Berrick & Skivenes, 2012; Chateauneuf et al., 2018; Collings & Wright, 2022; Hedin, 2015; Sliedrecht et al., 2022; Wilson et al., 2000) indicated that relationships between birth and foster parents can oscillate between negative and positive, based on the existence and specifics of their interactions. These interactions are affected by each party’s knowledge, attitude, level of emotional stability, and level of comprehension and acceptance of the situation. Better contact and communication seem to be related to greater emotional intelligence, confidence in self and in others, social skills, kindness, respect, empathy, and consistent and thoughtful use of communication technologies. Thus, one implication is that birth and foster parents should benefit from socio-behavioral skills training. This is consistent with a conclusion drawn by Saarnik (2021) from her systematic literature review: foster parents need to be well prepared in terms of communication and behavioral competency for their interactions with both the child and the birth parents. Moreover, this is congruent with Noordegraaf and Nijnatten’s (2022) finding that regular communication via instant messages, for instance, is important because it can help birth and foster parents to match dialogue, exchange information, and ultimately build and maintain a cooperative relationship.

Four articles addressed the expected and unexpected roles played by birth and foster parents (Höjer, 2009; Pinto & Luke, 2022; Salem & Wilde, 2022; Weitz & Karlsson, 2021). These studies showed that defining the content of the relationship—being clear with birth and foster parents what to do and not do during foster care—is essential for the maintenance and success of their relationship. This revealed to us that successful relationships appear to be associated with both parties knowing exactly how to respect and correctly perform their roles. As a result, both birth and foster parents should be well informed about their roles, what is and is not expected of them. They should also understand, respect, and support the other party’s role to mitigate underlying power imbalances that undermine shared parenthood, as stated by Cannaert and Wilde (2024). This necessity for role clarification was also pointed out by Blythe et al. (2014) in their integrative review of foster parents’ experience. The authors found that foster parents displayed various perspectives about their role, which seemed to result in a variety of emotional and behavioral difficulties. Therefore, social services should provide communication and cooperation training to both birth and foster parents, encouraging a sense of true coparenting early in the foster care.

Finally, five articles (Broady et al., 2010; Fuentes et al., 2019; Gilligan, 1996; Sanchirico & Jablonka, 2000; Spielfogel & Leathers, 2022) indicated that the training and support that birth and foster parents perceive they have received from social services can influence their acknowledgment of the importance of their relationship For instance, when birth and foster parents perceive little or no support from social services, they tend to behave and interact in their own particular way, not knowing or not following the appropriate guidelines, which often leads to poor relationships between them. The better the training and support these parents perceive they have received, the more aware they are of the positive effects of relating to each other. As a consequence, they engage in more interparental activities. These findings are consistent with the results from a qualitative study performed by Healy et al. (2023), which showed that relationships between birth and foster parents tended to be poor or nonexistent, which seemed to be due to a lack of training and support. As noted in a qualitative study conducted by Nesmith et al. (2017), support by social workers has the power to increase and improve birth and foster parents’ interactions during visits. Similarly, Gouveia et al. (2021) indicated that social workers should be available to support the parents’ relationship and resolve any misunderstandings or conflicts that arise at any stage of the fostering process. They should also make it clear that although foster care has been legally mandated, no one is against anyone else and that all individuals involved, including their opinions and feelings, are equally important and must be considered.

Limitations and Future Directions

This study has highlighted relevant findings from a range of studies. Nevertheless, we must consider several limitations, especially regarding the number of existing studies on the subject of relationships between birth and foster parents, as well as the methodology, geographic distribution, samples, and purpose or content of these studies.

Only 22 studies were found to meet the inclusion and exclusion criteria. Most of the studies were qualitative (n = 16) and were carried out in European countries (n = 13), and a significant number (n = 10) involved only foster parents as participants. Furthermore, the reviewed studies often lacked descriptive and sociodemographic information about their samples. The studies that provided clear information regarding the number of mothers, fathers, and couples evidenced a tendency towards more female (n = 374) than male (n = 241) participants. Throughout our search and screening process, we found that research on this topic is limited and that the major focus of studies on the relationship between birth and foster parents is often the child’s physical and mental health. None of the included studies, for instance, compared the perceptions of the specifics of the relationship held by both parties in the same foster case in relation to the establishment and maintenance of their relationship. Also, we found no research that focused on the impact, quality or importance of the relationship between birth and foster parents and the well-being of birth and foster parents (or vice versa).

This is consistent with the limitation found by Blythe et al. (2014), which is that, despite foster parents’ influence on children’s outcomes, there is little research on their experiences and the effects on themselves of providing foster care. For Miller et al. (2019), foster parents’ stressors, specifically relational/social stressors and those related to the foster child, finances, and the child welfare system, are crucial to the self-care and, subsequently, to their attitudes and behaviors towards the other parties (e.g., birth parents). To our knowledge, and based on our search, similar research has not been done on birth parents. We did not find detailed information regarding, for example, the frequency, context, and content of the relationships between birth and foster parents that might give us a better understanding of this phenomenon.

As a result, future research should include additional quantitative, qualitative, or mixed methods studies, as well as studies with birth parents and with the birth and foster parents of the same child. These studies would allow us to learn more about birth and foster parents’ perceptions of their relationship with one another. To learn more, particularly regarding the quality of these relationships, it would be beneficial to develop or adapt measures of coparenting relevant to the context of foster care (e.g., the Family Functioning Style Scale [FFSS], developed by Dunst et al., 1988; the Coparenting Relationship Scale [CRS], developed by Feinberg et al., 2012; the Coparenting Questionnaire [CQ] developed by Margolin et al., 2001).

Moreover, it would be helpful to analyze the impact of frequency, context, and content on birth and foster parents’ perceptions of their positive or negative relationships with each other. The number of times they communicate, the place(s) where they meet, and what is shared influence their opinions on the type of relationship they have. All these factors can play a key role in the gradual improvement of the psychosocial services provided to these families, thus contributing to their well-being and satisfaction. Also, we suggest researching, developing or adapting, and disseminating intervention and training programs (e.g., The Connections Project, developed by Gerring et al., 2008; Incredible Years, adapted to foster care by Linares et al. 2006a, b). This may help address the scarcity of research on foster parent training, as evidenced by Kaasbøll et al. (2019) in their systematic literature review.

In addition, this systematic review had limitations due to our methodological decisions. First, studies that focused specifically on kinship foster parents were excluded; however, given that kinship implies a prior relationship between birth and foster parents, it may be important to explore these relationships. Second, the limited number of databases used for the research, the consideration of only peer-reviewed journal articles, and the lack of manually searched articles that could have arisen from the primary research should be noted. Third, three possible languages (English, Portuguese, and Spanish) were allowed in the inclusion criteria but the search terms were only in English. Fourth, there is a risk of bias associated with subjective interpretation of inclusion and exclusion criteria, which we minimized by using peer coding. We recognize the possibility that we did not find all the studies that are relevant to this topic. We also acknowledge that registering the systematic review protocol (e.g., in PROSPERO) would have enhanced the methodological rigor of the study. Finally, we used thematic synthesis in this heterogeneous and subjective field. Even though this is an appropriate method given the aim of this systematic review and the articles’ characteristics, we recognize that the themes may not be entirely independent and could be interrelated. To overcome these limitations, future systematic reviews should expand the search to other databases, such as PsychINFO, use combinations of terms in languages other than English during the initial search, and adjust the inclusion and exclusion criteria. These decisions may contribute to a more inclusive approach and avoid missing potentially relevant studies.

Conclusion

This systematic literature review has provided important data regarding several factors that influence the relationships between birth and foster parents. The main themes that emerged were birth and foster parents’ intentions and efforts to cooperate, quality of contact and communication, role expectations, and perceptions of professional support. The review also highlighted some limitations in the research. To address these limitations, more quantitative and mixed methods studies are necessary to overcome the subjectivity involved in reporting the results from most of the reviewed studies. Also, additional qualitative studies are required to extend our knowledge of the perceptions of birth and foster parents (ideally of the same child) on the importance and functional details of their relationship. The findings of this study have significant implications for child and family welfare services, health professionals, and decision-makers as they provide a framework for future research and interventions, which can lead to the improved psychosocial well-being of all parties involved in foster care.