A multicenter intervention cluster study with a randomized controlled trial is being conducted in the north metropolitan area of Barcelona, Spain, between 2023 and 2026. It is implemented in the public universal primary care system, specifically from the reproductive and sexual health care units (ASSIRs; Catalan: Atenció a la Salut Sexual i Reproductiva) [28,29] and in the territory’s reference public hospitals for childbirth care. The participating centers were randomly assigned (primary care and their reference hospitals).

The study population is composed of pregnant women from the ASSIR centers, where pregnancy monitoring is conducted, with deliveries planned in the reference hospitals. Participants were enrolled in order of care, provided they met the inclusion criteria and had been accepted into the study, until the predetermined sample size was reached. The inclusion criteria were as follows: (1) receiving care in these ASSIRs and hospitals; (2) being aged 16 years or more, with a gestational age between 24 and 32 weeks; and (3) wishing to breastfeed. The exclusion criteria were as follows: (1) linguistic barriers that prevented the understanding of the information and the ability to complete the questionnaires and (2) not wishing to participate. Participants were followed from 24 to 32 weeks of gestation to 6 months post partum. The follow-up period lasted until September 2025.

We followed the guidelines of the Declaration of Helsinki regarding bioethical principles of clinical research. This research protocol was approved by the research ethics committee of the Jordi Gol Primary Care Research Institute as well as the reference hospitals participating in this study: Hospital Parc Taulí, Hospital General de Granollers, Hospital Germans Trias i Pujol, and Hospital de Mataró. The final version of this protocol (22/101-P) was approved and signed on February 22, 2023.

Data collected through questionnaires on REDCap (Research Electronic Data Capture; Vanderbilt University) are encrypted and stored in a secure database. Data for the study were collected directly from project participants based on their prior written consent, in accordance with the provisions of Articles 6.1.a and 9.2.a of the General Data Protection Regulation.

A total of 126 participants is needed in each group to detect a statistically significant difference between the 2, assuming a confidence level of 95% and a power of 80% in a 2-tailed test, according to the calculations of the GRANMO sample size and power calculator (version 8.0; Datarus). Based on the data published in 2019 on the population studied, the EBF rate at 6 months would be 17% in the control group (CG) and 34% in the experimental group (EG) [21]. The loss to follow-up rate is estimated to be 20%. A total of 252 participants will be studied, with 126 (50%) in each group.

All data were collected through questionnaires completed by the researcher in charge of participant recruitment, using the REDCap secure web application [30] housed in the Catalan Health Institute.

A range of variables were collected to enable the computation of outcome measures used to evaluate the effectiveness of the intervention (refer to the Data Analysis Plan section).

The timing of participants’ data collection is presented in Table 2, and the variables (more details are provided in Multimedia Appendix 1) are presented in Textbox 1.

Data collection by time, place, and the instruments used are presented in Table 2.

The effectiveness of the educational intervention will be evaluated as differences between the EG and CG across 3 principal outcome variables. These outcomes are derived from the data collected during the study and are structured from general descriptive indicators to specific interventional impacts.

Categorical variables (such as gender, country of birth, and infant feeding type) will be summarized using absolute and relative frequencies for the total and categories.

Quantitative variables will be described using means and SDs for normally distributed data and medians and 95% CIs for nonnormally distributed data.

The differences will be checked with the chi-square test for categorical variables and ANOVA for continuous variables with normal distribution or the Kruskal-Wallis H test for continuous variables with nonnormal distribution. The statistical significance will be set at P<.05. The registers with missing data for main outcome variables will not be included in the analysis.

The timeline and implementation status of phase 2 of the Green Mother project are mentioned subsequently.

Mothers involved in breastfeeding and parenting will collaborate with the research team to evaluate and validate the content of informational pamphlets and other resources of the proposed educational interventions before implementation. Their opinions will also be considered for discussion of the project results and their subsequent dissemination to communities and the public.

Starting with the objective of evaluating the effectiveness of this educational and reinforcing intervention, we expect to find the following differences between the 2 groups:

It is crucial to adopt evidence-based strategies and new guidelines for complementary education in aspects such as breastfeeding, mothers’ nutrition, and environmental information for the health personnel involved in the care of pregnant and breastfeeding women.

Group education, both written and audiovisual dissemination, has proven to be an effective tool used by primary care professionals. The self-determination of women and their partners as providers of food for the entire family and their role in obtaining sustainable food must be reinforced.

Once the project is completed, the guide, different materials, and courses will be used to train all health professionals in the entire territory of Catalonia involved in mother and baby care to focus on the nursing mother, providing the best conditions for a good start to breastfeeding and offering support for any difficulties that may arise. It will also include information on how to follow a healthy and environmentally friendly diet.

Prenatal counseling and education in primary care centers will be updated with the materials created for this project, and they will be disseminated to all health centers. Potential limitations of the study during data collection are that participants in the CG, without specific intervention, can obtain information through social networks, television, and the internet. However, to control for this fact, we included a final questionnaire to verify the sources of information.

In this study, all participants intending to breastfeed are included, as its objective is not to influence their decision of which type of infant feeding, they choose but rather to support those who wish to breastfeed for an extended period (6 months), helping them achieve this successfully and without complications. For the infant feeding rates in the general case, we conducted phase 1 of the Green Mother project, and from the previous study, LACTEM [21], from the same geographic area, we found that 96% of the pregnant mothers wanted to breastfeed. The mothers’ illness, country of birth, and age were also observed as facilitators of and barriers to breastfeeding. During the recruitment phase 1 of this project, which investigated the environmental impact of different types of infant feeding, we observed a 93% breastfeeding rate at hospital discharge [12].

Furthermore, all users with the intention of breastfeeding are included because the objective of this study is not to influence the type of breastfeeding that the participants will choose but rather to ensure that those who want to breastfeed for a long time can achieve it. This also helps to see the rates of those who wanted but could not initiate or follow the EBF or breastfeeding.

The development of this research will not only enable the updating of standard prenatal programs but also contribute to the achievement of the Sustainable Development Goals (SDGs), particularly those related to health (SDG 3), gender equality (SDG 5), responsible consumption (SDG 12), and climate action (SDG 13). Ultimately, strengthening health education through an environmental lens may foster a shift in attitudes toward healthier and more sustainable practices, thereby ensuring the long-term well-being of both the population and the planet [25,26].

The results of this study will demonstrate the effectiveness of the educational and counseling intervention. This intervention will not only help improve support for prolonged breastfeeding and therefore benefit children’s health but also help reduce environmental impact, raising awareness among mothers and families of the importance of breastfeeding their children and having healthy and sustainable diets, as stated in the 2030 SDGs.

The findings of this project will be shared with both the scientific community and the public through various channels. These include continuing education courses, informative talks, community discussions, as well as presentations at conferences and congresses. By disseminating the results through these media, the knowledge gained from the project will reach a broader audience and contribute to the advancement of understanding in the field and the achievement of the SDGs.