This quantitative study uses an observational analytic design using the cross-sectional method. This study looks for the relationship between the independent variables, namely gender, Early Breastfeeding Initiation (IMD), exclusive breastfeeding, breastfeeding status, and Minimum Dietary Diversity (MDD), with the dependent variable, namely the incidence of stunting in children aged 6-23 months. The population of this study were children aged 6-23 months in West Java Province who were sampled in the 2021 SSGI study. The sample determination was carried out using a purposive sampling technique with the criteria that children aged 6-23 months in West Java Province had complete data related to age, gender, body length measurements, and breastfeeding and complementary feeding. The sampling technique resulted in 2,670 samples of children aged 6-23 months in West Java Province. The data used in this study were obtained through the 2021 Indonesian Nutrition Status Study (SSGI) documentation, including age, sex, length/height, length/height measurement method, early breastfeeding initiation, exclusive breastfeeding, breastfeeding status, and MDD.

The Indonesian Nutrition Status Study 2021 as the main data source in this study has been granted ethical approval by the Health Research Ethics Commission, Badan Penelitian dan Pengembangan Kesehatan (KEPK-BPPK) with letter number LB.02.01/2/KE.248/2021.

In this study, information on MDD was assessed based on SSGI data, a recall of foods consumed by children under two years of age in the last 24 hours. MDD was measured using eight food groups: breast milk, rice, roots, and tubers; nuts and seeds; dairy products; meat; eggs; vitamin-A-rich fruits and vegetables; and other fruits and vegetables. Children under two years of age are considered to meet the MDD if they consume at least 5 of the eight food groups on the last day. Each child under two years of age will get 1 point for each food group consumed so that the MDD score will range from 0 to 8. The results are then categorized into two categories, namely "Met" if consuming ≥ 5 food groups (total score ≥ 5) and "Not met" < 5 food groups (total score < 5).

The research data were analyzed through univariate analysis by presenting the frequency distribution of the respondents' characteristics, bivariate analysis using a chi-square test using 5% alpha and 95% Confidence Interval, and multivariate analysis using a logistic regression test.

The findings in this study are that there is an association between gender and the incidence of stunting in children under two years of age. This study shows that boys under the age of two have a 1.25 times higher risk of stunting than girls. This result is in line with the findings of Yuningsih and Perbawati (2022), who found a significant association between sex and stunting (p=0.04) and supports the view that sex is a biological risk factor for stunting (Thompson, 2021). A meta-analysis by Thurstans et al. (2020) also showed that malnutrition, such as stunting, wasting, and being underweight, is more common among boys.

Biologically, males have only one X chromosome, which carries immune-critical microRNAs, making them more susceptible to adverse mutations and primary immune deficiencies (Libert et al., 2010; Schurz et al., 2019). Sexual hormone differences also affect the immune system, where testosterone produced due to the SRY gene on the Y chromosome can inhibit the immune system and increase lean body mass and basal metabolism (Fischer et al., 2015; Thompson & Michelle, 2013).

Systemic inflammation due to infections that males are more susceptible to can decrease the production of IGF-1 and IGFBP, which play a role in bone growth, thereby increasing resistance to growth factors (DeBoer et al., 2017; Wu et al., 2015). In addition, higher energy requirements lead to earlier weaning and earlier introduction of complementary foods for male infants, which also increases the risk of stunting (Bork & Diallo, 2017).

Early Breastfeeding Initiation (IMD) is important because it involves skin-to-skin contact and colostrum ingestion. Skin-to-skin contact can prolong the duration of breastfeeding, increase the likelihood of exclusive breastfeeding, and help with body temperature regulation and the transfer of good bacteria from mother to baby (Moore et al., 2016; Pannaraj et al., 2017). Colostrum, rich in growth factors and immune components such as IgA and lactoferrin, is essential for developing the infant's immune system (Ballard & Morrow, 2013; Munblit et al., 2016). Since infants cannot produce their own IgA, a lack of IgA from breast milk can lead to disturbances in the gut microbiota and inflammatory diseases (Guo et al., 2021). High systemic inflammation can also decrease IGF-1 and IGFBP production, triggering resistance to growth factors (DeBoer et al., 2017).

This study found no significant association between IMD and stunting, which aligns with the findings of Nsereko et al. (2018). This discrepancy may be due to the IMD indicator, which only detects skin-to-skin contact, not colostrum or breastfeeding (WHO & UNICEF, 2021). Not all infants can breastfeed within the first hour, and maternal recall may be biased due to labor complications (Carter et al., 2021). Nonetheless, the risk of stunting in infants without IMD was recorded to be 1.034 times higher. Infants without IMD are more susceptible to hypoglycemia, hypothermia, and metabolic acidosis, which can lead to IGF-1 resistance and impaired bone growth (Bulbul & Uslu, 2016; Zaki & Shanbag, 2023).

Exclusive breastfeeding provides essential nutrients for infant growth and immunity during the first 6 months, but this study found no significant association between exclusive breastfeeding and the incidence of stunting. Similar results were found by Tello et al. (2022), who stated that there was no significant association between exclusive breastfeeding and stunting in children under 2 years of age. Interestingly, this study showed that children not exclusively breastfed appeared to be more protective against stunting (ORc=0.813, 95% CI 0.659-1.002).

This may be due to the different indicators used. The WHO defines the exclusive breastfeeding indicator as children aged 0-5 months who were only breastfed in the last 24 hours (WHO & UNICEF, 2021), but this study's indicator was children who were introduced to liquids/foods other than breast milk at ≥ 6 months of age. While this indicator may avoid bias from pre-lacteal feeding, it has the disadvantage of a long recall period and the risk of inaccurate data (Alayón et al., 2022). Previous studies have shown that recall of exclusive breastfeeding after 6 months has low sensitivity and specificity due to maternal overestimation (Bland et al., 2003). It is also possible that although infants were not introduced to foods other than breast milk until ≥ 6 months of age, they did not receive adequate breast milk before that.

Zong et al. (2020) also found that there was no significant difference in the body length of infants aged 1-6 months who were or were not exclusively breastfed, and children aged 6-12 months who remained breastfed had a lower mean body length than those fed formula. This may be influenced by the post-birth decline of natural growth hormones and the role of genetic factors and complementary feeding practices in the second half of life.

This study found a significant association between breastfeeding status and incidence of stunting, where children under two years old who were no longer breastfed were more protective against stunting than those still breastfed (ORc=0.693; 95% CI 0.533-0.901). This finding aligns with Jones et al. (2014), who reported a negative association between continuous breastfeeding and stunting, and Nsereko et al. (2018), who showed breastfeeding for more than 1 year as a predictor of stunting because it delays complementary feeding. However, these results do not necessarily mean that better breastfeeding practices increase the risk of stunting, as mothers with malnourished children or living in highly malnourished communities may breastfeed more intensely (Tello et al., 2022). In food insecurity, high breastfeeding may help maintain a child's weight and height through body fat accumulation (Skau et al., 2019). The breastfeeding indicator in this study is not sensitive as children may be breastfed irregularly, as supported by the last 24 hours recall data (Sankar et al., 2015). WHO and UNICEF recommend continued breastfeeding until 2 years or older (WHO & UNICEF, 2021), while the AAP states that breastfeeding can be continued as long as both mother and baby are comfortable (American Academy of Pediatrics, 2012). In Islam, breastfeeding until the child is 2 years old is recommended as long as it does not harm the mother or child (Ismail, 2018).

Children aged 6-23 months should be given varied complementary foods to meet nutritional needs because breast milk alone is insufficient (UNICEF, 2016). Limited stomach capacity leads to small but rich portions of essential nutrients, and dietary diversity is associated with linear growth (Onyango et al., 2014). WHO recommends Minimum Dietary Diversity (MDD) as measured by eight food groups; children are considered to meet MDD if they consume at least five groups daily (WHO & UNICEF, 2021). Appropriate feeding practices, including the type, timing, amount, and consistency of food, are important to reduce the risk of malnutrition and stunting (UNICEF, 2020a). Food consistency should be gradual from soft to solid, as inappropriate texture or dilution of complementary foods can reduce energy intake (Koletzko et al., 2019). The frequency and amount of food are adjusted according to the child's age and breastfeeding status (UNICEF, 2020a).

This study found no significant association between MDD and stunting, in line with Gassara et al. (2023). Dietary quality is also assessed through Minimum Acceptable Diet (MAD) and Minimum Meal Frequency (MMF), which were not analyzed in this study due to data limitations, possibly leading to bias (Mya et al., 2019; Sankar et al., 2015). However, the risk of stunting was 1.022 times higher in children who did not meet the MDD. Dietary diversity predicts diet quality and micronutrient density (Bandoh & Kenu, 2017; Prado & Dewey, 2014).

Animal foods such as meat, milk, eggs, and poultry are rich in essential micronutrients such as vitamins A, B-12, iron, and zinc, which are difficult to obtain from plants alone (Dror & Allen, 2011). Dairy products support growth through their complete nutritional content (Judit, 2020). Vitamin A is important for growth and immunity but is associated with malnutrition (Abedi et al., 2015). Grains and cereals are also sources of energy and nutrients that help reduce undernutrition (Khamis et al., 2019). Lack of consumption of nutrient-dense foods such as eggs, milk, fruits, and vegetables at 6-23 months of age increases the risk of stunting (Aguayo & Menon, 2016).

This study has limitations due to the weakness of the breastfeeding indicators and does not consider the frequency or quantity of breast milk and complementary foods. The recall period for IMD and exclusive breastfeeding variables tends to be long, which may lead to inaccurate data. In addition, the 24-hour recall in the MDD variable cannot eliminate the possibility of inconsistent food diversity.