Development and Validation of the Breastfeeding Literacy Assessment Instrument (BLAI) for Obstetric Women.

Citation: Valero-Chillerón, M.J.; Vila-Candel, R.; Mena-Tudela, D.; Soriano-Vidal, F.J.; González-Chordá, V.M.; Andreu-Pejo, L.; Antolí-Forner, A.; Durán-García, L.; VicentFerrandis, M.; Andrés-Alegre, M.E.; et al. Development and Validation of the Breastfeeding Literacy Assessment Instrument (BLAI) for Obstetric Women. Int. J. Environ. Res. Public Health 2023,20, 3808. https:// doi.org/10.3390/ijerph20053808 Academic Editor: Vieri Lastrucci Received: 20 January 2023 Revised: 18 February 2023 Accepted: 20 February 2023 Published: 21 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). International Journal of Environmental Research and Public Health Article Development and Validation of the Breastfeeding Literacy Assessment Instrument (BLAI) for Obstetric Women María Jesús Valero-Chillerón1, Rafael Vila-Candel 2,3,4,* , Desirée Mena-Tudela 1,* , Francisco Javier Soriano-Vidal 2,4,5,6, Víctor M. González-Chordá1,7 , Laura Andreu-Pejo 1, Aloma Antolí-Forner 1, LledóDurán-García1, Miryam Vicent-Ferrandis 8, María Eugenia Andrés-Alegre 3 and Águeda Cervera-Gasch 1 1Department of Nursing, Universitat Jaume I. Av de Vicent Sos Baynat, 12071 Castelló, Spain 2Department of Nursing, Universitat de València, 46007 Valencia, Spain 3Department of Obstetrics and Gynaecology, Hospital Universitario de la Ribera, 46600 Valencia, Spain 4Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO-SP), 46020 Valencia, Spain 5Department of Nursing, University of Alicante, 03080 Alicante, Spain 6Department of Obstetrics and Gynaecology, Hospital Luis Alcanyis, 46800 Xàtiva, Spain 7Nursing and Healthcare Research Unit (Investén-Isciii), Institute of Health Carlos III, 28029 Madrid, Spain 8Department of Maternity, Hospital General Universitario, 12004 Castelló, Spain *Correspondence: [email protected] or [email protected] (R.V.-C.); [email protected] (D.M.-T.) Abstract: Background: Despite international efforts to protect and promote exclusive breastfeeding (EBF) for infants up to six months of age, global rates of EBF continue to fall short of the targets proposed by the WHO for 2025. Previous studies have shown a relationship between the level of health literacy and the duration of EBF, although this relationship was not determinant, probably due to the use of a generic health literacy questionnaire. Therefore, this study aims to design and validate the first specific breastfeeding literacy instrument. Methods: A Breastfeeding Literacy instrument was developed. Content validation was carried out by a group of 10 experts in health literacy, breastfeeding or instrument validation, obtaining a Content Validity index in Scale (S-CVI/Ave) of 0.912. A multicentre cross-sectional study was carried out in three Spanish hospitals to determine the psychometric properties (construct validity and internal consistency). The questionnaire was administered to 204 women during the clinical puerperium. Results: The Kaiser-Meier-Oklin Test ( KMO = 0.924 ) and Bartlett’s Test of Sphericity (X 2 = 3119.861; p ≤ 0.001) confirmed the feasibility of the Exploratory Factor Analysis, which explained 60.54% of the variance with four factors. Conclusions: The Breastfeeding Literacy Assessment Instrument (BLAI) consisting of 26 items was validated. Keywords: breastfeeding; breastfeeding literacy; questionnaires; validation study 1. Introduction Pregnancy and the postpartum period constitute an important stage in women’s health, in which a series of events take place that require special attention and monitoring by the health system. Although it is a physiological process, it involves a continuum of decision-making in which women need to have sufficient information so that these decisions protect and promote not only their health, but also that of their children. One of the most important decisions to be made is regarding the feeding the infant will receive. International organisations such as the World Health Organisation and UNICEF recommend exclusive breastfeeding (EBF) for the first six months of an infant’s life and breastfeeding with complementary foods until at least two years of age [ 1 ]. The promotion of EBF is an international target in different programmes such as the Comprehensive Implementation Plan on Maternal, Infant, and Young Child Nutrition of the World Health Assembly [ 2 ], the United Nations Decade of Action on Nutrition 2016–2025 [ 3 ], and the Int. J. Environ. Res. Public Health 2023,20, 3808. https://doi.org/10.3390/ijerph20053808 https://www.mdpi.com/journal/ijerph Int. J. Environ. Res. Public Health 2023,20, 3808 2 of 14 investment framework of the World Bank [ 4 ]. However, despite multiple efforts to protect breastfeeding (BF), rates of EBF at six months of infant life remain very low, at around 38% globally [ 5 ]. Furthermore, laws to protect breastfeeding remain inadequate in most countries [ 6 ]. In Europe, the six-month EBF rate is around 25% [ 7 ]. However, in Spain, the six-month EBF rate has varied from 16.8% in 2019 [ 8 ] to 39% in 2017 [ 9 ]. The data need to be interpreted with caution as the variation in these data is caused by the absence of a unified approach for collecting and monitoring BF information in Spain. The premature discontinuation of breastfeeding is a complex phenomenon that is influenced by a multitude of factors, including demographic characteristics (e.g., young maternal age, low levels of education and socio-economic status), social considerations (e.g., inadequate workplace support), psychological determinants (e.g., maternal intentions before birth, self-assurance, and engagement in breastfeeding), as well as biological considerations (e.g., infant health concerns, maternal health issues, first-time motherhood, and issues related to lactation) [ 10 – 13 ]. These considerations contribute to the multifaceted nature of early breastfeeding cessation. However, several studies have shown that, in many cases, early weaning occurs due to maternal decisions or perceptions, which do not always correspond to reality [ 14 ]. In the face of these false perceptions, health literacy (HL) has a fundamental role because the primary outcome of having a good level of HL is the ability to make good decisions that promote and protect health [15]. Various authors have broadly defined the concept of HL over time [ 16 ]. Despite the lack of consensus on constructing a single definition of this concept, most authors agree that it is multidimensional, complex, and heterogeneous [ 17 ]. Sørensen et al. proposed an integrated model of HL that looked at cognitive and social skills that enable the individual to address four competencies (access, understand, appraise, and apply health information) and three domains in which the individual interacts with the health system (health care, disease prevention, and health promotion) [18]. This complex concept of HL has been reformulated and adapted to specific health areas or populations. As a result, it is possible to retrieve a multitude of validated instruments that allow us to generically assess the level of HL, such as the European Health Literacy Survey Questionnaire (HLS-EU-Q) [ 19 ] or the test of functional health literacy in adults (TOFHLA) [ 20 ]. There are also instruments available that focus on measuring literacy in specific health areas, such as the Literacy Assessment for Diabetes (LAD), which addresses diabetes literacy [ 21 ]. Others focus on specific populations, such as the eHealth Literacy Scale (eHEALS), which addresses electronic health literacy in a young population [ 22 ]. It is also possible to retrieve the Maternal Health Literacy Inventory in Pregnancy (MHELIP) instrument, which is designed to measure maternal health literacy [ 23 ]. However, to our knowledge, no previous instrument has measured breastfeeding literacy (BFL). Recent studies have suggested that an adequate level of HL may be a protective factor against early BF cessation [ 12 , 13 , 24 ]. However, these studies use generic HL instruments to determine the relationship between HL and the specific health domain of BF. Specifically, they use the Short Assessment of Health Literacy for Spanish-speaking Adults (SAHLSA) [ 24 ] and the Newest Vital Sign (NVS) in its validated version for Spanishspeaking populations [ 12 , 13 , 24 ]. The main findings of using a generic instrument to explore a particular area of health lack specificity and concreteness in the results obtained, so the authors agree on the need for a specifically validated instrument to measure the level of BFL in women during the perinatal stage [12,13,24]. Therefore, this study aims to design and validate a specific instrument to measure the level of BFL. 2. Materials and Methods 2.1. Design, Setting, and Participants A design and validation study of the Breastfeeding Literacy Assessment Instrument (BLAI) was conducted to assess the level of BFL in a Spanish context. The study took place from 1 December 2021 to 30 September 2022. Int. J. Environ. Res. Public Health 2023,20, 3808 3 of 14 The project was designed under Organic Law 03/2018, of 5 December, under the Protection of Personal Data and Guarantee of Digital Rights. First, the instrument was designed by reviewing the literature and content validity by creating a panel of experts. Second, a cross-sectional study was carried out on women during the clinical postpartum period in three hospitals in the Valencian Community (Spain): Hospital Universitario de La Ribera (HULR); Hospital General de Castellón and Hospital Lluís Alcanyís de Xàtiva (Spain) to determine the psychometric properties of the BLAI. Inclusion criteria were: having given birth in one of the participating hospitals and voluntarily agreeing to participate in the study. Exclusion criteria were: having a linguistic barrier that impeded understanding and completion of the data collection form, multiple gestations, or the neonate being admitted to a neonatal care unit. Participants completed an online informed consent form prior to data collection. The Ethics and Research Committees of each participating hospital approved the study. Furthermore, the principles of the Declaration of Helsinki were respected throughout this effort. According to Anthoine et al.’s recommendations for instrument validation, a sample size of between five and ten participants per instrument item is recommended [ 25 ]. Thus, given that the initial version of the instrument had 28 items, a sample of between 140 and 280 participants was required. However, according to Ferrando y Anguiano-Carrasco, a minimum sample size of 200 participants is recommended to assess the quality of a questionnaire [ 26 ]. Therefore, a sample size of at least 200 participants would be sufficient to satisfy both criteria. A non-probabilistic convenience sampling was performed, in which a data collection form was administered consisting of sociodemographic variables (age, country of origin, educational level, perceived socioeconomic status), obstetric variables (parity, feeding doubts before birth, previous BF, variables related to previous BF experience), and the BLAI. 2.2. Questionnaire Development and Content Validity The BLAI was designed based on the definition of the HL concept adapted to the BF context. It was therefore organised into the following dimensions: D1: Access to breastfeeding-related information; D2: Understanding of such information; D3: Appraise the veracity of information related to breastfeeding; D4: Application of that information. The formulation of the items was based on the difficulty in dealing with the situations described, establishing a Likert-type scale with four response options to avoid central tendency errors. The items were developed based on the integrated model of health literacy proposed by Sørensen et al. [ 18 ]. This model considers the dimensions mentioned above and applies them to healthcare, disease prevention, and health promotion. Likewise, it considers the perspective of the individual’s capacity and the interaction that the individual has with the social and health environment. Following the development of the first battery of items, a panel of nine experts in breastfeeding, health literacy, and questionnaire development and validation, which included midwives, lactation consultants, and research nurses, was formed. The initial iteration of the survey instrument was presented to a panel of experts for an evaluation of its overall relevance, the appropriateness of individual items within the context of each dimension, and the identification of other item-specific feedback. As many rounds as necessary were carried out until an average congruence percentage (ACP) of 0.9, as recommended by the literature, was reached [ 27 ]. For this purpose, the Item Content Validity Index (I-CVI) was calculated using the methodology proposed by Polit and Beck, with considerations given to the level of validity of each item, the probability of agreement due to chance (Pc), and the modified Kappa coefficient [ 27 ]. In addition, the overall scale average (S-CVI) was calculated, which determines the mean of the scores of all the I-CVIs and reflects the overall validity of the instrument. Int. J. Environ. Res. Public Health 2023,20, 3808 4 of 14 2.3. Psychometric Properties After content validation, the instrument was administered to women in the participating hospitals during the clinical postpartum period, provided they voluntarily agreed to participate in the study. First, a descriptive analysis of the sample was carried out using the mean, standard deviation, and 95% confidence interval for quantitative variables and absolute and relative frequencies for qualitative variables. After this initial analysis, construct validity was studied using an exploratory factor analysis (EFA). For this purpose, the factor extraction method used was principal axis factorisation, applying an oblique factorial rotation, given the potential correlation between the different factors. The ProMax rotation method was used since a dominant factor was not considered. Previously, the feasibility of the EFA was confirmed with the Kaiser-Mayer-Olkin (KMO) test and Bartlett’s test of sphericity. A factor loading greater than 0.4 was considered to retain items in a given factor [ 28 ]. The dimensionality of the instrument was studied using the Kaiser criterion, which considers as many factors as eigenvalues greater than 1 are present [29]. Second, the instrument’s internal consistency and dimensions were determined. Since an ordinal response scale was used, McDonald’s Omega was employed (adequate internal consistency of ω = 0.7–0.9) [ 30 ]. Due to the non-normality of the overall scores for each dimension, Spearman’s correlation coefficient was used to investigate the relationship between the different elements of the instrument. A range between 0.50–0.70 was considered a good correlation, and >0.7 was a strong correlation [31]. 2.4. Inferential Analysis After studying the instrument’s psychometric properties, an inferential analysis was carried out to explore the association between the level of BFL and the rest of the variables included in the study, using Chi-squared or Fisher’s exact test, depending on the nature of the variables. Participants were first grouped by determining the cut-off points for each of the dimensions of the BLAI questionnaire using cluster analysis. The k-means method was used, forcing two groups to differentiate between inadequate and adequate BFL levels, obtaining statistically significant differences between the two groups. Statistical analysis was carried out with SPSS v.26, considering a statistical significance level of p< 0.05. 3. Results 3.1. BLAI Validation Results An ACP of 0.864 was achieved for content validity through the panel of experts (n= 9) after the first round. The experts’ contributions to reformulating some items were greatly valued; they added new items to cover certain aspects not contemplated and changed the dimension of others. After conducting a second round, the authors obtained an ACP score of 0.913, which met the percentage recommended by relevant research. After this second round, only minor modifications were made to the wording of the items, resulting in a version of the instrument consisting of 28 items (Access six items; Understand five items, Appraise ten items, Apply seven items). The wording of the items is available in the supplementary material (Table S1), both in the original version in Spanish and in the translated version (not validated) in English. Regarding the modelling of the instrument through exploratory factor analysis (EFA), it was observed that two items (Access6 and Appraise6) obtained a poor factor loading (<0.4) in the dimension for which they were developed. Moreover, according to theoretical reasoning, these two items had no place in another dimension. In addition, the instrument’s internal consistency slightly increased when these items were removed, so they were eliminated from the instrument, which went from 28 items to 26 items. Regarding the new 26-item version, KMO (0.924) and Bartlett’s Test of Sphericity ( X2= 3119.861 ;p ≤ 0.001) confirmed the feasibility of the EFA. The factor analysis explained 60.54% of the variance with a total of four factors, coinciding with the theoretical design Int. J. Environ. Res. Public Health 2023,20, 3808 5 of 14 of the instrument. Specifically, the first factor (Access) explained 44.02% of the variance and consisted of five items, the second factor (Apply) explained 8.04% of the variance and comprised seven items, the third factor (Appraise) explained 4.38% of the variance and consisted of nine items, and the fourth factor (Understand) explained 4.09% of the variance and consisted of five items. The overall reliability of the questionnaire ( ω = 0.949) and of each of the dimensions (Access ω = 0.809; Understand ω = 0.810; Appraise ω = 0.912; Apply ω = 0.873) was excellent. Table 1shows the results of the content validity, exploratory factor analysis, and reliability of the BLAI. Table 1. Content validity, Exploratory Factor Analysis, and reliability of BLAI. Content Validity Index Factors Communalities 1234ω1 Access 0.907 0.809 Access1 1.00 0.676 0.399 0.311 0.402 0.948 0.490 Access2 1.00 0.748 0.403 0.419 0.401 0.948 0.560 Access3 1.00 0.687 0.318 0.356 0.411 0.948 0.505 Access4 1.00 0.656 0.367 0.391 0.552 0.948 0.563 Access5 0.67 0.565 0.405 0.445 0.557 0.947 0.534 Understand 0.956 0.810 Understand1 1.00 0.426 0.460 0.551 0.529 0.947 0.476 Understand2 1.00 0.645 0.520 0.552 0.602 0.946 0.615 Understand3 0.89 0.713 0.422 0.473 0.615 0.947 0.601 Understand4 0.89 0.587 0.399 0.404 0.707 0.947 0.557 Understand5 1.00 0.494 0.485 0.480 0.725 0.947 0.526 Appraise 0.856 0.912 Appraise1 0.89 0.510 0.601 0.673 0.741 0.946 0.715 Appraise2 0.78 0.508 0.580 0.634 0.679 0.946 0.654 Appraise3 0.78 0.340 0.665 0.696 0.676 0.946 0.608 Appraise4 1.00 0.338 0.639 0.703 0.603 0.946 0.584 Appraise5 0.67 0.330 0.513 0.771 0.396 0.947 0.589 Appraise7 1.00 0.394 0.549 0.801 0.525 0.947 0.654 Appraise8 0.89 0.423 0.610 0.749 0.605 0.946 0.616 Appraise9 0.89 0.489 0.590 0.692 0.616 0.946 0.625 Appraise10 0.78 0.371 0.708 0.729 0.555 0.946 0.653 Apply 0.968 0.873 Apply1 1.00 0.380 0.706 0.618 0.645 0.946 0.611 Apply2 1.00 0.446 0.669 0.573 0.456 0.947 0.521 Apply3 1.00 0.471 0.587 0.472 0.607 0.947 0.481 Apply4 1.00 0.410 0.852 0.625 0.510 0.946 0.691 Apply5 1.00 0.485 0.776 0.587 0.494 0.946 0.618 Apply6 0.78 0.255 0.582 0.484 0.550 0.948 0.479 Apply7 1.00 0.335 0.692 0.482 0.537 0.947 0.534 1Internal Consistency measured with MacDonald’s Omega. As also shown in Table 1, the structure matrix demonstrates that most items obtained a higher factor loading for the dimension they were designed for, except for the following seven items that showed a considerable factor loading for two different dimensions. The formulation of the Understand1 item does not fit into the Appraise dimension. The formulation of the Understand3 item could be considered in both the Access and Understand dimensions, although the theoretical reasoning gives it more weight in the Understand dimension. The wording of the Understand2 and Understand4 items means they do not fit into the Access dimension. Finally, Appraise1, Appraise2, and Apply3 cannot be included in the Understand dimension. Int. J. Environ. Res. Public Health 2023,20, 3808 6 of 14 Regarding the correlation between the different dimensions, it is observed that all the correlations are good. Specifically, the correlation between the Appraise-Understand and Appraise-Apply dimensions is strong, as they are all statistically significant (Table 2). Table 2. Correlation matrix between the dimensions of BLAI. Access Understand Appraise Apply Access 1.000 Understand 0.680 1.000 Appraise 0.546 0.707 1.000 Apply 0.535 0.662 0.761 1.000 Rho de Spearman; All correlations are significant at the <0.001 level (bilateral). Table 3shows the minimum and maximum scores obtained in each dimension according to the cluster analysis carried out to differentiate between inadequate and adequate BFL. In addition, the descriptive analysis of BLAI for each of the dimensions can also be observed, in which it can be seen that the majority of the participants are in the category of Adequate BFL in all the dimensions, with the Understand dimension having the lowest percentage of women with Adequate BFL (54.9%, n= 112) and the Apply dimension having the highest percentage of women with Adequate BFL (66.2%, n= 135). Table 3. Cut-off points between inadequate and adequate BFL and descriptive analysis of BLAI. Inadequate BFL Adequate BFL p3 Min Max n1%2Min Max n% Access 1.8 3.00 82 40.2 3.20 4.00 122 59.8 <0.001 Understand 1.8 3.00 92 45.1 3.20 4.00 112 54.9 <0.001 Appraise 1.44 2.78 70 34.3 2.89 4.00 134 65.7 <0.001 Apply 1.29 2.71 69 33.8 2.86 4.00 135 66.2 <0.001 1Absolute frequencies; 2Relative frequencies; 3Cluster analysis. BFL = breastfeeding literacy. 3.2. Descriptive Analysis A total sample size of 204 participants was reached. The mean maternal age was 32.8 years (SD = 5.143; 95% CI 32.09–33.51). A total of 45.59% (n= 93) of the deliveries were attended at HULR, 83.8% (n= 171) of the women were originally from Spain, 50.5% (n= 103) had a university education, and 85.3% (n= 174) reported having a medium socioeconomic status (Table 4). Regarding the type of breastfeeding at discharge, 74% (n = 151) of the women chose Exclusive Breastfeeding (EBF), 6.4% (n= 13) mixed breastfeeding, and 19.6% (n= 40) chose formula feeding. Table 5shows variables related to the type of breastfeeding chosen during the puerperium. It was observed that 72.7% (n= 80) of primiparous women chose EBF. Of the women who opted for EBF, 82.3% (n= 135) had no doubts about the type of breastfeeding, while 38.5% (n= 15) did have doubts during gestation, although they finally chose EBF. Only one woman reported opting for EBF due to pressure from her environment. As for the general perception of the previous BF experience (n= 82), 52.4% (n= 44) perceived it as a very good experience, and nine of them (10.7%) reported having a regular previous BF experience. Only 45.3% (n= 38) felt supported at all times by healthcare professionals, and 39.3% (n= 33) felt supported at all times by family and friends. The 63.4% (n= 52) fed EBF up to six months or more to their previous child. As for a reason for giving up breastfeeding, 36.9% (n= 31) of the cases were physiologically weaned, while 20.3% (n= 17) were weaned because they had started working. Int. J. Environ. Res. Public Health 2023,20, 3808 7 of 14 Table 4. Sociodemographic Characteristics. n1%2 Hospital H. Universitario de La Ribera 93 45.6 H. General Universitario de Castellón 88 43.1 H. Lluís Alcanyís de Xàtiva 23 11.3 Country of origin Spain 171 83.8 Central and South America 20 9.8 Rest of European Union Countries 9 4.4 Other 1 0.5 Educational level Primary studies 33 16.2 Professional training 68 33.3 Degree, bachelor’s degree 68 33.3 Master’s degree or Phd 35 17.2 Perceived socioeconomic status Low 26 12.7 Middle 174 85.3 High 4 2 1Absolute frequencies; 2Relative frequencies. Table 5. Descriptive analysis of obstetric and breastfeeding-related variables. Exclusive Breastfeeding Mixed Feeding Formula Feeding n1%2n%n% Parity First 80 39.2 6 2.9 24 11.8 Second 55 27 5 2.5 11 5.4 Third or more 16 7.8 2 1.00 5 2.5 Feeding doubts before birth I had no doubts 135 66.2 6 2.9 23 11.3 I had doubts, but it was my own free will 15 7.4 7 3.4 17 8.3 I had doubts, I felt pressured 1 0.5 - - - - Previous BF Yes 70 34.3 5 2.5 7 3.4 No 81 39.7 8 3.9 31 15.2 General perception of previous breastfeeding experience (n= 82) Very good 43 51.2 1 1.2 - - Good 18 21.4 2 2.4 2 2.4 Regular 9 10.7 1 1.2 3 3.6 Bad - - 1 1.2 4 4.8 Professional support received during previous breastfeeding (n= 82) Supported at all times 33 39.3 2 2.4 3 3.6 Supported most of the times 12 14.3 2 2.4 2 2.4 Supported sometimes 8 9.5 1 1.2 1 1.2 Insufficient support 17 20.2 - - 3 3.6 Support from family and friends received during previous breastfeeding (n= 82) Supported at all times 28 33.3 1 1.2 4 4.8 Supported most of the times 20 23.8 3 3.6 3 3.6 Supported sometimes 6 7.1 1 1.2 - - Insufficient support 16 19 - - 2 2.4 Int. J. Environ. Res. Public Health 2023,20, 3808 8 of 14 Table 5. Cont. Exclusive Breastfeeding Mixed Feeding Formula Feeding n1%2n%n% Months exclusively breastfed during previous breastfeeding (n= 82) 1 month or less 4 4.8 3 3.6 8 9.5 2–3 months 8 9.5 - - - - 4–5 months 8 9.5 - - 1 1.2 6 months or more 50 61 2 2.4 - - Main reason for abandonment of previous breastfeeding (n= 82) Previous BF has not ended 6 7.1 - - - - Physiological weaning 31 36.9 - - - - Breast problems unrelated to BF 1 1.2 - - 2 2.4 Breast problems related to BF 2 2.4 - - 2 2.4 Lack of professional support 1 1.2 1 1.2 - - Lack of family support 1 1.2 - - 1 1.2 Work incorporation 15 17.9 2 2.4 - - Perceived lack of breastmilk 8 9.5 - - 4 4.8 Reduced infant weight gain 5 6 2 2.4 - - 1Absolute frequencies; 2Relative frequencies; BF: breastfeeding. 3.3. Breastfeeding Literacy Assessment Instrument Table 6shows that as the perceived socioeconomic level increases, the percentage of participants with adequate Access BFL increases (p= 0.016). It can also be seen that the percentage of women with adequate Understand BFL or adequate Apply BFL is higher in those women who offer EBF (Understand: 59.6%, n= 90, p= 0.023; Apply: 70.9%, n= 107, p= 0.026), while those who opted for mixed breastfeeding obtained a lower percentage (Understand: 23.01%, n= 3, p= 0.023; Apply: 38.5%, n= 5, p= 0.026). Regarding the Appraise dimension, the percentage of Adequate Appraise BFL is lower among primiparous women (p= 0.022), and the highest percentages are observed among multiparous women of second (78.9%, n= 56) or subsequent gestations (65.2%, n= 15), with the differences being statistically significant (p= 0.018). Regarding the Apply dimension, the percentage of women with Adequate Apply BFL is higher among multiparous women of second gestation (77.5%, n= 55), followed by primiparous women (60.9%; n= 67). Multiparous women of third or later gestations were the ones with the lowest percentage of Adequate Apply BFL. A comparative analysis of sociodemographic and BF-related variables for each of the dimensions of the BLAI questionnaire can be found in the supplementary material (Tables S2–S5). Table 6. Statistically significant associations with the dimensions of the BLAI questionnaire. Inadequate BFL Adequate BFL p-Value n1%2n% Access Socioeconomic status 0.016 3 Low 16 61.5 10 38.5 Middle 66 37.9 108 62.1 High - - 4 100 Understand Lactation type 0.023 4 Exclusive Breastfeeding 61 40.4 90 59.6 Mixed Feeding 10 76.9 3 23.1 Formula feeding 21 52.5 19 47.5 Int. J. Environ. Res. Public Health 2023,20, 3808 9 of 14 Table 6. Cont. Inadequate BFL Adequate BFL p-Value n1%2n% Appraise Previous Breastfeeding 0.022 4 Previous Breastfeeding 22 26.8 60 73.2 No previous Breastfeeding 12 27.3 32 72.7 Is my first pregnancy 35 46.1 41 53.9 Parity 0.011 4 First 47 42.7 63 57.3 Second 15 21.1 56 78.9 Third or more 8 34.8 15 65.2 Apply Parity 0.042 4 First 43 39.1 67 60.9 Second 16 22.5 55 77.5 Third or more 10 43.5 13 56.5 Lactation type 0.026 4 Exclusive Breastfeeding 44 29.1 107 70.9 Mixed Feeding 8 61.5 5 38.5 Bottle feeding 17 42.5 23 57.5 1Absolute frequencies; 2Relative frequencies; 3Fisher’s exact test; 4Chi-squared; BFL: breastfeeding literacy. 4. Discussion The BLAI presents adequate psychometric properties to assess BFL levels in women during the perinatal period, with adequate construct validity and internal consistency. The exploratory factor analysis explains 60.54% of the variance with four domains, coinciding with the four dimensions covered by the concept of HL (Access, Understand, Appraise, and Apply) developed by Sørensen et al. [18]. It is worth mentioning that, during the instrument’s modelling, a number of items had a slightly higher loading in dimensions for which they were not designed. However, after thoroughly examining each item to evaluate the feasibility of assigning it to alternative dimensions, the research team determined that it was more appropriate to retain these items within their original dimensions, as the theoretical alignment was more convincing in these dimensions. In addition, two items were removed (Access6, Appraisse6) due to their poor factor loadings. The internal consistency of the BLAI slightly increased after their deletion. As for the dimensionality study of the instrument, the EFA was run without determining a number of factors to extract, allowing the statistical programme to determine the number of factors based on the Kaiser criterion of eigenvalues greater than 1 [ 29 ]. This is the default method in the statistical programme used, and it is possible to retrieve scientific evidence that casts doubt on its practical usefulness, as has been reported by other authors [ 32 , 33 ]. However, the resulting factor structure coincided with the number of dimensions for which the instrument was created. Today, there are other, more commonly used methods to corroborate the appropriate number of factors, such as parallel analysis or the ratio of the first-to-second eigenvalue. However, we have not found a universally accepted criterion. For example, in the case of eigenvalues, there is no criterion for the ratio to be accepted, some authors propose four [ 34 ], others five [ 35 ], but none seem to be based on empirical reasoning. Therefore, it is essential that future studies consider other analyses for studying dimensionality. While it is true that the use of a single criterion may lead to an overestimation or an underestimation of the actual number of factors, over-extraction leads to fewer measurement errors [ 36 ]. Moreover, it would not be appropriate to treat as unidimensional