Substance use among pregnant and parenting women is increasingly recognized as a growing global public health concern [1,2]. Prevalence rates vary considerably across studies, shaped by sociodemographic characteristics, national legislation, and the reliability of self-reporting and disclosure practices [3,4]. These variations, compounded by methodological challenges and underreporting, make it difficult to establish accurate estimates [5,6]. Nonetheless, recent data suggest that substance use during pregnancy affects 4%-15% of all women [3]. In the United States, approximately 6% of women use illicit substances during pregnancy [7], and about 10% consume alcohol while pregnant [8]. Additionally, nearly 1 in 10 children younger than 6 years lives with an adult who has a substance use disorder (SUD) [9,10]. In Europe, substance use during pregnancy is reported in 6.5%‐11% of cases [11], while the prevalence of parental SUD ranges from 6.2% to 35.2% [12]. In Belgium, a recent study found that 14.6% of women consume alcohol, 4% use tobacco, and 0.4% use illicit substances during pregnancy, with substantial variation across trimesters [13]. Accurate data on parental substance use remain unavailable due to major data gaps and fragmented registration systems. However, recent figures indicate that approximately 22% of individuals entering treatment live with minors, although it is unclear whether these minors are their biological children, their partner’s children, or younger siblings [14]. Furthermore, a 2015 study suggested that 12% of children live with parents who misuse alcohol, while fewer than 1% live with parents who use illicit drugs [15].

The risks associated with substance use during the perinatal period are multifaceted and far-reaching. Physiologically, teratogenic risks are well documented. Most substances cross the placental barrier, affecting the uterus, the placenta, and fetal development [16]. Psychosocially, substance use problems are often associated with parenting challenges. Mothers with substance use problems often exhibit lower sensitivity and more passive, harsh, or disengaged behaviors during interactions with their infants, and they often lack essential parenting knowledge and have inappropriate development expectations [17,18]. Difficulties in forming a healthy parent-child relationship are common and may be partly explained through the neurobiological overlap between SUD and attachment systems [18]. Moreover, other factors often contribute to poor parenting behaviors, including maternal childhood trauma, co-occurring mental health disorders, exposure to intimate partner violence, increased vulnerability to parenting stress, homelessness, and a lower socioeconomic status [17-20].

Beyond the developmental and relational consequences for the child, substance use during the perinatal period also poses substantial risks to maternal health and well-being. Pregnancy increases vulnerability to interpersonal violence due to heightened physical, emotional, and financial demands [21]. Overdose has become one of the leading causes of preventable death among postpartum women with substance use problems, contributing to a tripling of drug-related pregnancy-associated mortality in recent years [22,23]. Moreover, since the perinatal period may also be a source of increased stress [24]—physical, psychological, and societal—many women continue to use substances during pregnancy [25], and relapse among those who initially reduce or cease use is most common in the third trimester [26] or early postpartum period [25,27-30]. Notably, research has suggested that up to 80% of women who are abstinent in the last month of pregnancy relapse within the first 2 years postpartum [28].

These risks often result in child welfare involvement. Over the past 2 decades, parental SUD has become a major factor in out-of-home placements [31,32]. It is estimated that between 50% and 80% of children in foster care have at least one parent with SUD [33]. However, maternal and infant trajectories vary widely. Some mothers retain custody, others experience separation, and some are later reunited. The relationship between maternal SUD and child removal is not straightforward [34].

Still, the perinatal period is characterized by high motivation to initiate behavioral change, seek treatment, and engage in recovery [11,17,35]. After all, many women cease or reduce their substance use during pregnancy [28,30,36]. Their motivations are rooted in the desire to ensure a healthy pregnancy and birth outcome, improve personal well-being, and avoid child welfare involvement [9,30,31,35]. The perinatal period thus represents a critical phase of growth and transformation [30] and is often described as a “window of opportunity” [21,27,37,38]. For caregivers, the increased frequency and intensity of contact with health care and support services during this time offer a unique opportunity to build trust and establish long-term care trajectories [9,39]. However, despite this potential for positive change, navigating the perinatal period is particularly demanding for these women. In addition to the physical, emotional, and psychological changes experienced by all pregnant and postpartum women, they must manage their own addiction and/or recovery while dealing with the challenges of pregnancy or parenting, which may be further complicated by the effects of prenatal substance exposure and the scrutiny of legal, social, and moral systems [2,40].

This paradox of the perinatal period encompassing both vulnerability and potential transformation underscores the need for a deeper understanding. Yet, research examining how these dynamics interact in the context of perinatal substance use remains scarce. The phenomenon is often concealed due to stigma and underreporting [41], and most information is derived from cross-sectional surveys and retrospective reports [28]. The limited prospective studies available primarily focus on the relapse process in this period or the medical effects of prenatal substance exposure on the child [28,33,42], and have generally adopted a deficit-based approach. Few studies have systematically examined the trajectories of women navigating both motherhood and substance use, specifically exploring how they make meaning of experiences and the factors that contribute to a successful transition to parenthood among women with substance use problems.

The PIPPA (Perinatal Insights into Parenting, Pathways, and Addiction) study (May 2025 to November 2026) aims to address this gap through a longitudinal observational design that adopts a strengths-based approach, which emphasizes that individuals possess capacities, resources, and potential for change, even in the context of significant adversity [43]. This approach aligns with the recovery paradigm in addiction, which highlights connectedness, hope, personal agency, meaning, and empowerment as key elements supporting the recovery process [44,45].

Conducted in Flanders, the Dutch-speaking region of Belgium, the study follows pregnant and parenting women with substance use problems throughout the perinatal period. It examines perinatal psychosocial factors, contextual influences, and recovery capital to understand how these elements relate to parental development and the evolving trajectories of both mother and child.

The central research question is as follows: Which maternal, psychosocial, and contextual factors influence whether the perinatal period represents a promising or challenging transition to parenthood for pregnant and parenting women with substance use problems, and how do the trajectories of mother and child unfold in the short and long term? Additional subquestions include the following: (1) What are the sociodemographic, substance use, pregnancy, parenthood, and psychosocial characteristics of women with substance use problems, and how do they describe their experiences during the perinatal period? (2) How do maternal mental health, recovery capital, substance use, and mother-child relationship quality evolve across the perinatal period, and how are these trajectories related to substance use severity? (3) Which maternal, psychosocial, and behavioral factors predict custody retention, cohabitation, and recovery opportunities during the perinatal period?

The PIPPA study is a longitudinal, prospective, multicenter, mixed methods study following pregnant and parenting women with substance use problems throughout the perinatal period. For the purpose of this protocol, the topic is limited to pregnant and parenting women; this terminology is not intended to exclude or overlook the experiences of people of other genders who may also experience pregnancy and parenthood.

Participants are assessed at 2-3 points: during pregnancy, between 2 and 6 weeks postpartum, and at 6 months postpartum (Figure 1). In cases where mothers are enrolled after giving birth, the prenatal assessment is logically omitted.

The PIPPA study aims to gain more insight into the transition to motherhood for pregnant and parenting women with alcohol and/or other substance use problems by exploring the maternal, psychosocial, and contextual factors that shape their experiences during pregnancy and the first 6 months of motherhood. Given the sensitivity of the topic and the fragile circumstances of many of these women, we aim to recruit 50 pregnant and parenting women within 1.5 years, with a follow-up period of 6 months. This sample size was determined in consultation with the various centers that provide services to this hard-to-reach population and is expected to provide adequate power for descriptive, longitudinal, subgroup, and regression analyses, depending on the specific research question and statistical method (see the Data Analysis Plan section).

Participants are recruited across Flanders through multiple service sectors (Table 1). Recruitment takes place in clinical settings, specifically the gynecological and obstetric departments of 7 general and university hospitals. In addition, both residential and outpatient substance use treatment centers are involved. These include general substance use services, such as 3 low-threshold multidisciplinary Medisch-Sociaal OpvangCentra (low-threshold harm-reduction centers), which focus on harm reduction and provide medical care, psychosocial support, and social reintegration, as well as Verslavingskoepel vzw, where experts by experience voluntarily provide support and guidance together with professional care providers. Moreover, several specialized initiatives that specifically target pregnant and parenting women with substance use problems are involved. Two of these facilities, Antwerps Drug Interventie Centrum – Ontwenningsprogramma ouders en kind (Antwerp Drug Intervention Center – Detoxification program for parents and children) and De Kiem (Therapeutic community, Tipi), provide residential treatment, while others, such as vzw Kompas (Drugspecifieke thuisbegeleiding voor gebruikende ouders met jonge kinderen [Substance-specific home-based support for substance-using parents with young children]) and Free Clinic (Gezinnen onder invloed Antwerpen [Families under the influence Antwerp]), offer outreach and ambulatory support. Furthermore, 2 perinatal support networks (Perinataal Ondersteuningsnetwerk Druggebruikende Ouders [Perinatal support networks for drug-using parents]) participate in the recruitment. These initiatives bring together health care, substance use, and child protection services to support pregnant and parenting women who use substances, with the primary aim of safeguarding the child’s well-being through early, coordinated, and family-centered care. Additional recruitment occurs through child protection services in the Flemish provinces of East and West Flanders, which are mandated to safeguard children’s well-being and may intervene when parental substance use poses risks to children’s safety. Finally, participants are also recruited through social media campaigns on Facebook, LinkedIn, and Instagram, which inform both caregivers and pregnant and parenting women about the study’s aims, inclusion criteria, and contact options (email, phone, QR code, or direct message).

The eligibility criteria for pregnant and parenting women include (1) being in the second or third trimester of pregnancy or in the early postpartum period, (2) being older than 18 years and younger than 45 years, (3) having regularly used illegal substances (including cannabis) and/or consumed excessive alcohol (>10 units per week) [46,47] in the past year (counted from 6 months prior to pregnancy), (4) being able to communicate in Dutch or English, and (5) being willing to participate in 2-3 assessments. During pregnancy or shortly after birth, women are informed about the aims and design of the PIPPA study through flyers and by staff members of the collaborating facilities. At the initial meeting with the researcher, they receive detailed information about the study and the implications of study participation and are asked to provide written informed consent.

Participants are also asked if an involved professional caregiver who plays an important role in their trajectory may be contacted. With the participant’s consent, this caregiver is approached for a semistructured interview at each assessment point. The eligibility criteria for these caregivers include (1) being able to communicate in Dutch or English, (2) having an individual counseling relationship with the pregnant and parenting women, and (3) being willing to participate in 2-3 assessments. The exclusion criteria are (1) being involved only in the obstetric aspects of the process and not in the psychosocial aspects, and (2) having no further follow-up after pregnancy.

Working with a hard-to-reach and often vulnerable population presents several methodological and practical challenges. The process of recruiting and retaining participants is particularly complex due to challenging life circumstances; existing stressors of pregnancy; multiple appointments with care providers; and barriers such as limited mobility, fear of stigma, and custody concerns [48,49]. To address these difficulties, this study incorporates recommendations for recruiting and retaining pregnant women in longitudinal research through the following five levels of socioecological influence [48,49]:

This multilevel strategy is designed to enhance recruitment, reduce drop-out, and maximize feasibility in a complex and vulnerable population.

Following separate analyses, quantitative and qualitative findings will be integrated within a convergent parallel mixed-methods design using joint displays and narrative weaving [71], aligning quantitative trajectories with qualitative themes at both the case and pattern levels to identify convergence, divergence, and complementarity. This integration will allow us to identify how quantitative patterns align with, extend, or contrast participants’ lived experiences.

This study received ethical approval from the Medical Ethics Committee of the University Hospital Gent on April 16, 2025 (UZGent; ONZ-2024‐0603). Participants are informed about the confidentiality of the data they provide, and written informed consent is acquired from all participants prior to inclusion in the study. Participants receive a €15 (US $17.47) voucher for each completed assessment. All data are treated confidentially and reported anonymously. This study is conducted in accordance with the Declaration of Helsinki.

This protocol describes the design of the PIPPA study, a longitudinal, mixed-methods investigation into the transition to parenthood among women with substance use problems. Drawing on a convergent parallel mixed-methods design [71], the study integrates maternal self-reports and caregiver perspectives to generate an in-depth understanding of the psychosocial and contextual factors shaping short- and long-term maternal and child trajectories.

The PIPPA study is expected to generate insights into how the perinatal period may function as a promising or challenging transition to parenthood for pregnant and parenting women with substance use problems. Drawing on prior research, several anticipated findings may emerge. First, we anticipate substantial heterogeneity in women’s characteristics and substance use patterns across the perinatal period. Recent studies have described distinct classes regarding perinatal substance use and illustrated how pregnant and parenting women in these classes differ in social context, socioeconomic circumstances, and mental health [79]. By capturing this heterogeneity longitudinally and from both maternal and caregiver perspectives, the PIPPA study will clarify how different perinatal substance use trajectories unfold over time. A better understanding of this diversity may inform the development of tailored, responsive, and equitable care approaches for pregnant and parenting women with substance use problems [2,79].

Second, greater severity of substance use is expected to be associated with poorer maternal mental health, lower recovery capital, and less optimal mother-child relationship quality. Prior research links depressive and posttraumatic stress disorder symptoms to increased craving, a higher risk of relapse, and lower prenatal bonding [27,28,80]. Studies have shown that higher substance use severity predicts elevated depressive symptoms postpartum [27]. Recovery capital research has further consistently demonstrated that limited personal, social, and community resources predict worse outcomes and increased relapse risk [45], while supportive networks are protective [81]. Developing greater insights into how these factors relate to and interact with one another across pregnancy and the postpartum period can guide more individualized, context-sensitive support for pregnant and parenting women. Moreover, by examining these factors simultaneously and longitudinally, the PIPPA study can offer a better understanding of how these factors reinforce each other and how women understand and experience the interplay among mental health, substance use, and recovery.

Third, maternal mental health, substance use, and recovery capital are likely to fluctuate across the perinatal period, with many women experiencing the most pronounced distress around 6 months postpartum. This aligns with evidence showing the impact of increased parental stress, limited support, intimate partner violence, identity transition demands, and cumulative vulnerabilities documented among pregnant and parenting women with substance use problems [28,45,82,83]. Prior studies indicate that relapse rates are high during the postpartum period [27-29,83,84], and virtual models predict that by 2 years postpartum, all women who were abstinent during pregnancy resume substance use [28], which may disrupt the mother-child relationship [27]. The longitudinal follow-up in the PIPPA study will make it possible to map how and why needs evolve, providing evidence on long-term needs that have been largely missing from previous, shorter-term studies.

Finally, custody retention and cohabitation outcomes are anticipated to relate strongly to maternal mental health, relational stability, the availability of a supportive network, and substance use patterns. Evidence shows that pregnant and parenting women with substance use problems are at a higher risk of child removal when facing intimate partner violence, unstable housing, untreated mental health difficulties, or polysubstance use [2,29,85,86]. These findings suggest that custody outcomes are shaped less by the mother-child bond itself and more by maternal well-being and contextual stability. By linking maternal well-being, relational stability, recovery capital, and substance use patterns to custody trajectories, this study will help identify which factors primarily shape cohabitation outcomes and which areas of support may meaningfully improve the likelihood of family preservation. Moreover, by tracing diverse trajectories and documenting not only vulnerabilities but also sources of strengths, such as recovery capital and contextual support, the PIPPA study will contribute to a more nuanced and strengths-based understanding of perinatal substance use.

We plan to disseminate the study findings through peer-reviewed publications, presentations at national and international conferences, and contributions to study days and symposia, thereby strengthening the scientific evidence on perinatal substance use. Additionally, through collaborations with professional networks and interdisciplinary meetings (such as the Perinet expert group on addiction; Vlaams expertisecentrum alcohol en andere drugs [Flemish Center of Expertise on alcohol and other drugs]; and residential mother-child rehabilitation units, including Tipi and Antwerp Drug Intervention Center), the study aims to translate findings into practice-oriented insights for professionals. Furthermore, we will develop accessible summaries tailored for participants and the wider public. These will be shared through involved organizations, care providers, and social media platforms.

Several methodological limitations must be acknowledged. First, the relatively modest sample size may limit statistical power and the ability to detect subtle effects or conduct subgroup analyses. This challenge is amplified by the substantial variability in maternal and child trajectories, which may complicate between-group comparisons. Second, reliance on self-reported measures of substance use and psychosocial variables introduces potential biases, including social desirability and recall biases. Given the stigma surrounding perinatal substance use and concerns about child-welfare involvement, underreporting remains a realistic possibility.

A further limitation concerns the risk of attrition in a population characterized by instability and shifting life circumstances. Although multiple retention strategies are implemented, dropout may still occur and must be considered when interpreting longitudinal outcomes.

Despite these challenges, several features of the PIPPA study strengthen its methodological rigor and interpretative depth. The mixed-methods approach enables the integration of quantitative data with qualitative insights, allowing for meaningful interpretation even when quantitative data are limited or incomplete. Although the expected sample size is modest, it is relatively large for this population and offers a valuable opportunity to explore experiences that are rarely captured in research. The inclusion of women across a broad spectrum of substance use, from ongoing substance use to use in the 6 months before conception, allows for a nuanced understanding of perinatal substance use and highlights opportunities for tailored or less intensive forms of support. Additionally, methodological triangulation, combining quantitative assessments with in-depth interviews of pregnant and parenting women and caregivers, provides comprehensive, multiperspective insights into maternal and child trajectories.

Moreover, this study adopts a strengths-based approach, framing the perinatal period as a window of opportunity [27,37] and focusing on how pregnant and parenting women make meaning of change, pregnancy, and parenthood. This approach moves beyond deficit-oriented perspectives and highlights factors that promote positive transitions to motherhood. The longitudinal design, following pregnant and parenting women from pregnancy through 6 months postpartum, addresses a significant gap in existing research [28].

Lastly, the study’s socioecological engagement and retention strategy [48,49], addressing individual, interpersonal, organizational, community, and policy-level barriers to participation, represents a major methodological strength. This multilayered approach increases feasibility and supports sustained involvement in a population for whom research participation can be particularly challenging [49,50]

The PIPPA study is designed to advance the understanding of how maternal, psychosocial, and contextual factors shape the transition to parenthood for pregnant and parenting women with substance use problems. By integrating longitudinal quantitative data with maternal narratives and caregivers’ perspectives, this study aims to capture the heterogeneity of women’s experiences and trajectories, and the complex interplay among substance use, mental health, recovery capital, and early parenting. Anticipated findings, such as fluctuations in maternal mental health, variations in substance use and recovery trajectories, and the influence of social support, mirror patterns reported in previous research. The insights generated are expected to contribute to a more nuanced, strengths-based, and evidence-informed understanding of the perinatal period as a promising or challenging transition to parenthood for pregnant and parenting women with substance use problems, which may inform and strengthen integrated and responsive early interventions.