Based on the study findings, prevalence of wasting, underweight, stunting, and overweight, were respectively 6, 4.3, 7.9, and 9.2% among the studied children less than 5 years old. In a study conducted by Farrokh-Eslamlou et al., prevalence of wasting, underweight and stunting in less than 5 years old children of West Azerbaijan were respectively 5.7, 3.7, and 8.7% that these findings are almost in line with the findings of the present study [14].

Various studies have been conducted on the prevalence of malnutrition and investigation of anthropometric indices among Iranian children, but most of these studies are at the provincial level or a city, and studies conducted at the national level are limited [15]. Also, the estimates of the prevalence of malnutrition based on anthropometric indices in variety studies is different, which makes it difficult to compare the findings of present study with the findings of these studies. For example in the study conducted by Houshiar Rad et al., the prevalence of wasting, underweight, stunting, and overweight were obtained respectively 4.5, 7.6, 13.1, and 5.2% among the Iranian children less than 5 years old [16]. In the study conducted by Mohseni et al., the prevalence of wasting, underweight, and stunting were respectively 7.8, 10.5, and 12.4% [17]. Also, in the study conducted by Motedayen et al., the prevalence of wasting, underweight and stunting were respectively 6, 7 and 11% among the Iranian children less than 5 years old.

According to the report, in 2020 globally, 149.2 million children (22%) under the age of 5 were stunted, 45.4 million (6.7%) were wasted, and 38.9 million (5.7%) were overweight [18]. Also, in the study conducted by Ssentongo et al., in low- and middle-income countries, the prevalence of wasting, underweight and stunting among children under 5 years of age were 6.3, 13.7 and 29.1%, respectively [19].

Comparing the findings of the present study with the findings of the other studies [16,17,18,19], indicates the improvement of the situation of children in Urmia in terms of wasting, underweight and stunting over time, but it must be mentioned that although the percentage of malnutrition based on wasting, underweight and stunting indices is lower than other reports, but this problem still strongly remains. In particular, stunting index which has a higher percentage than wasting and underweight indices in this research. Stunting index, while indicating chronic malnutrition at the individual level, it is also one of the strongest indicators of hunger and poverty and can be a warning factor [4]. Therefore, it is recommended in nutrition improvement programs, in addition to improving the quantity and quality of nutrition and health services, poverty alleviation programs and the development of deprived areas must be implemented.

Moreover, according to this research’s findings, the prevalence of overweight among children under 5 years of age in Urmia is higher than other reports, for instance, in comparison with the study of Houshiar Rad et al., the prevalence of overweight among children under 5 years of age in Urmia has almost doubled [16] or almost tripled in comparison with the study of Emamian et al. [20]. Currently, there is an international agreement to achieve a rate of less than 5% for wasting, less than 6% for overweight and about 14.7% for stunting by 2025 [21]. Achieving these purposes needs designing and implementing various interventions, especially educational and nutritional interventions among children and mothers. In order to increase the effectiveness of these interventions, first, the factors influencing anthropometric indices must be determined in order to concentrate our interventions on those factors which are significantly related with these indices and can be changed via the intervention.

According to this research’s findings, one of the factors which had a statistically significant relationship with anthropometric indices, was the maternal nutritional literacy, so that the mean score of nutritional literacy among mothers with wasting, underweight and stunting child was lower than mothers with normal child. In line with the findings of the present study, in studies conducted by Fadare et al. [7], Oly-Alawuba et al. [9], and Saaka [8], there was a positive and significant relationship between maternal nutritional literacy with WAZ, HAZ, and WHZ indices of children, which confirm the findings of this study. In contrast to this study’s findings, in study conducted by Wanjihia et al. [22], there was no significant relationship between maternal nutritional literacy and WAZ, HAZ and WHZ indices of children. So, authors of article stated two reasons for justifying this finding: 1) In examining the relationship between maternal nutritional literacy and anthropometric indices, confounding variables were not controlled, 2) and also assessing the nutritional knowledge of mothers/caregivers was not based on local context or foods available locally [22].

According to this research’s findings and other research conducted [7,8,9], it can be concluded that maternal nutritional knowledge is still a fundamental factor and must be regarded in efforts aimed at enhancing anthropometric indices and eradicating malnutrition among children. Nutrition education is one of the interventions which can help enhance the maternal nutritional literacy. Therefore, designing and implementing educational programs applying existing theories and models in health education science with the purpose of enhancing mothers’ nutritional knowledge is recommended, implementing such interventions can finally lead to enhanced nutritional status and anthropometric indices of children [22]. But, it must be mentioned that maternal nutritional knowledge is not the only determinant of nutritional status and anthropometric indices of children, other factors may have an effect which must be determined and in efforts aimed at enhancing anthropometric indices among children, they must also be regarded.

Based on this research’s findings, the prevalence of underweight among children whose mothers had a college education was higher than children whose mothers did not have a college education and also among the children whose mother’s gestational weight gain was less than 7 kg and more than 16 kg, compared to children whose mother’s gestational weight gain was between 7 and 16 kg. Moreover, the prevalence of stunting among children whose family income was less than adequate living was higher than children whose family income was sufficient.

Based on this research’s findings, it can be concluded that high education and college education do not guarantee nutritional status and optimal weight in children and educational interventions related to children’s nutrition, even among mothers with college education, should be implemented. Thus, conflicting results were reported considering the relation between mother’s education level and child anthropometric indices. For instance, in the research conducted by Anzar et al., the results indicated that there was no significant relationship between maternal education level and WAZ and HAZ indices [23], while in the study conducted by Makoka et al., the results indicated that there was a positive and significant relationship between maternal education level with WAZ, HAZ and WHZ indices [24]. Therefore, more research are recommended to provide more correct results in this field.

Furthermore, according to this research’s findings, the mother’s gestational weight gain less than 7 and over 16 kg is a risk factor for underweight in children under 5 years of age, which it is required to be regarded and in preconception and prenatal education, mothers must be encouraged to have a normal weight gain and proportionate to their BMI during their pregnancy.

This research’s findings indicated that the prevalence of stunting among children whose family income was lower than the adequate level of life is higher than children whose family income was sufficient, this result was not far from expectation and is in line with the results of many studies in this field [22, 25]. Even in some research, it was noted that family income is a stronger factor in identifying children’s nutritional status than mothers’ nutritional knowledge [22]. Poverty and illiteracy are the top two leading causes of malnutrition and in nutrition improvement programs, priority should be given to disadvantaged, vulnerable and low-income groups [26].

Based on this research’s findings, the prevalence of wasting in the children 0–12 months was more than other age ranges. Consistent with this finding, in the study conducted by Aguayo et al., wasting prevalence was significantly higher among the children 0–11 months. The cause of this finding was attributed to poor complementary feeding practices in the first year of life which were not aligned with internationally agreed-upon guidance. Global and national policy recommends that infants aged 0–5 months be exclusively breast-fed, with no other fluids or foods given, not even water, while children aged 6–23 months should be fed age-appropriate soft, semi-solid or solid complementary foods while breast-feeding continues [27].

Also, the prevalence of underweight and wasting in males was higher than that of girls, which is in line with the study conducted by Ahmadi et al. (5). Moreover, among children with a history of acute respiratory infection and diarrhea during the past 2 weeks, the prevalence of underweight and wasting was significantly higher than among children without a history of these diseases, this result is not far from expectation and is in line with the results of other studies [5, 25].

Moreover, the prevalence of underweight and wasting was significantly higher among children who were currently consuming powdered milk and children who had not started complementary foods until after 6 months of age. Therefore, it is recommended to regard all these factors when designing and implementing interventions to enhance nutritional status and anthropometric indices of children, and focus our interventions more on mothers and children who have these risk factors, including mothers with low nutritional literacy, mothers whose gestational weight gain was not normal, children whose family income is low, children aged 0–12 months, boy child, children with a history of disease, children who consume powdered milk and children who have not started complementary foods at the right time.

One of the limitations of the present study was that the data related to maternal nutritional literacy, socio-economic and demographic variables were collected by a self-report method, so there was possibility that participants may have not given real answers to the questions.