The current study aimed to develop a theoretically-driven MBBC-6W and validate its reliability and validity in the Chinese population, which was achieved by following the systematic approach for scale development and comprehensive psychometric validation. In the stage of scale development, the initial 45-item scale was revised and reduced successively to the formal 36-item MBBC-6W through the pre-survey and item analysis. The final scale includes seven dimensions that were self-decision behavior (5 items), self-coping behavior (5 items), self-control behavior (5 items), resource coordination behavior (5 items), resource acquisition behavior (4 items), breastfeeding operation skills (6 items) and breastfeeding self-perception (6 items). All items of the scale are positive with Likert's five-point scale, and the scores are ranging from 36 points to 180 points. Meanwhile, the psychometric validation verified that the MBBC-6W had convincing internal reliability, external reliability, face validity, content validity, structure validity, convergence validity, distinguish validity, and calibration validity, meaning that it is a reliable and valid instrument to access mothers' breastfeeding behavior within six weeks postpartum.
The item was an essential part of the scale, and the items analysis was the critical step in scale development. In this study, five methods were used to analyze the capability of items from the perspectives of sensitivity, differentiation, internal consistency, representativeness, importance, and independence. The CV value reflected the sensitivity of items, and the finding represented that item 14 "For breastfeeding, I pay attention to own lifestyle (such as not drinking the strong tea, strong coffee, and alcoholic beverages, not smoking, not taking drugs, etc.)" had the poor sensitivity (CV < 0.15). The possible reason is related to the traditional Chinese puerperium culture, also known as "Zuo Yue Zi", which deems the lifestyle during the puerperium have a long-term impact on maternal health. Thus, most Chinese mothers and their social support system try their best to keep a healthy lifestyle in the puerperium [46]. The correlation coefficient of the scale scores and item 3 "I decided to breastfeed is not to meet the expectations of my husband, family or others" was lower than the standard, meaning item 3 could not represent the scale. The plausible explanation could be that, with the rise of female consciousness, modern independent women decide to breastfeed their infant because of the benefits for maternal and infant health, rather than to cater to other people [7]. The commonality of item 27 "I can recognize the sign of infant hunger accurately and timely" was less than the standard, presenting that the importance for scale was poor, which could be caused by maternal different understanding for "infant hunger sign". Item 28 "When breastfeeding, I will put the baby's face close to the breast, and align the tip of baby's nose at my nipple instead of mouth" and item 32 "For latch well, I support the breast with a C-shape (Place the thumb on top of the breast, and the other four fingers on the chest wall under the breast)" were deleted due to the lower commonality. The possible reason is the lower completion rate during breastfeeding, which is consistent with the maternal feedback during the daily clinical breastfeeding instruction. Both item 28 and item 32 were designed because the above-mentioned feeding techniques could help infants latch nipples well. The remaining item 33, "During the breastfeeding, my infant can always contain the whole nipple, and most of the areola in the mouth, " could evaluate the latch results more intuitively. Items 41 "I think I have sufficient breastmilk to meet infant demand" and item 43 " Breastfeeding makes me feel like a good mother", were deleted because of the cross-loading, indicating that the independence was not recognized. The deletion of item 43 may be related to it is a comprehensive variable without particularity. The perception of breast milk production is a manifestation of confidence, and the dimension of self-decision behavior also contains the item evaluating maternal confidence on breastfeeding, which may be the reason why item 41 belongs to both dimensions [47]. Fortunately, the measuring purpose of item 40 "I think breastfeeding made baby gain a healthy weight" is similar to item 41, and it could more objectively evaluate whether breast milk is sufficient.
Reliability, reflecting the internal consistency and stability of scale, includes internal and external reliability. The Cronbach's α coefficient and the split-half coefficient were used to verify the internal reliability. The results showed that Cronbach's α coefficient and split-half coefficient of scale were above reference, indicating that the scale has an excellent internal consistency according to the standard classification recommendation [48, 49]. The result showed that the re-test coefficient of the scale was exceeded the suggested value, meaning the scale has the capability for obtaining a stable result under similar external conditions and has acceptable external reliability [50]. The validity, referring to the ability of the scale to reflect the actual characteristics of the measuring target, consists of face validity, content validity, structure validity, convergence validity, distinguish validity, and calibration validity. In the pilot study, mothers with different education levels, delivery mode, parity, infant whereabouts were invited in the investigation, ensuring that comprehensive feedback was received from mothers with different characteristics, which provided a good condition to test scale applicability. Among them, most of the mothers (73.3%) had no doubts about items, and eight mothers pointed out some confusion in expression, which were subsequently resolved by the research group referring to maternal own suggestions thus the final revised scale was understandable with good face validity. Seventeen experts reviewed the content validity, and the findings showed that both item-level and scale-level CVI were acceptable, demonstrating that the MBBC-6W was compatible with the final measuring target. All of the methods often used to extract factors showed that the MBBC-6W yielded seven common factors, which matched the theoretical model. Moreover, the MBBC-6W could explain 68.852% of the total variance, confirming that the scale could capture the main characteristics of the mothers' breastfeeding behavior within six weeks postpartum. On the other hand, the results of CFA showed that, except that TLI is equal to 0.893, all of the remaining fitting indexes of the seven-factor model meet statistical requirements. However, the researcher pointed out that CFI is a valid reference when slightly smaller TLI than the standard value [51]. Therefore, although the value of TLI was less than 0.9, the CFI was equal to 0.903 indicating that the seven-factor MBBC-6W with acceptable structure validity. The factor loadings of items are more significant than the lower limit, indicating the item-belonging dimension with a good convergence validity. Moreover, the value of CR and AVE exceeded the reference, meaning that good convergence validity between different dimensions. Distinguish validity, reflecting the degree of distinction between different dimensions, were analyzed by the AVE method and Chi-square difference test in this study. Although the distinctive degree of F1, F2 and F3 were questioned in the result of the AVE method, the chi-square difference test confirmed that the original three-factor model was significantly better than one-factor model and the two-factor model, indicating that there was a distinction among F1, F2 and F3. The ROC analysis showed that both AUC was more significant than 0.7 when the scale was used to predict exclusive breastfeeding and any breastfeeding at 42 days, and they were not affected by covariances, suggesting that the scale was a valid tool to predict breastfeeding mode at 42 days. The MBBC-6W also exhibited specific correlations with MBFES and BSES-SF, further evidence that MBFES is a valid scale, as breastfeeding behavior is related to breastfeeding satisfaction and self-efficacy [52].
A new scale named MBBC-6W was developed and validated in this study, which was designed to measure breastfeeding behavior among the mothers within six weeks postpartum. Since there is no specific instrument to evaluate breastfeeding behavior, the current study has important theoretical and practical implications. In contrast to the existing scales, the scale is conceptually appealing because it directly concentrates on measuring behavior itself and innovatively focuses on the particular group of mothers within six weeks postpartum, which could lay a foundation for the evaluation and intervention in future research and clinical practice. However, due to the restrictions of time or own conditions, some limitations need to be considered. Firstly, the participants were recruited from the Fujian Maternity and Child Health Hospital, which might not represent the whole Chinese mothers' characteristics of breastfeeding behaviors within six weeks postpartum. Thus, the universality of the scale was limited, which could be enhanced through a multi-center investigation that included mothers of different races, cultures, geography, and medical institutions. Secondly, the convenient sampling method may affect the sampling representativeness, which could be improved through using random sampling in future research. Thirdly, even though a more extensive sample investigation was implemented, the sample size for EFA and CFA was insufficient because the sample was bisected for the credibility of factor analysis. Subsequent research should continue to expand the sample size to get a more stable and reliable model. Fourthly, the psychometric verification of MBBC-6W was based on the classical testing theory (CTT), which has inherent limitations, such as it is challenging to satisfy the assumption of error and accurate score. Further research should use the item response theory or multi-dimensional item response theory to overcome the limitation and provide more information for the psychometric testing of MBBC-6W. Finally, MBBC-6W has not yet been applied in clinical practice. The scale should be further used to investigate the current status and potential risk factors to help policymakers and health workers find problems and formulate corresponding strategies that are conducive to breastfeeding and achieve the goal of optimal breastfeeding practice ultimately.