The standardized chart (Z score) for weight, height, and head circumference indices in both groups showed the same pattern, which did not show a significant difference with the standardized child development pattern (WHO). Growth trend based on three indicators of average weight, height and head circumference for age in all periods of measurement showed better growth in boys than girls. (Table 1, Chart 1). According to the indicators of estimation of prevalence of underweight, wasting, short stature and microcephally, in all periods of monitoring, the male infants were is undesirable conditions as compared to female infants (Tables 2-5 and Charts 2-6).
Research findings indicated the proximity of the weightfor age index at birth in male and female infants studied in this research (Chart 1). To put it otherwise, no relationship has been observed between gender and birth weight. In the study conducted by Tusi et al., gender did not have any significant relationship with birth weight, height and head circumference. Furthermore, in the study conducted by Ali Malayeri (Jodipour) et al., in Sistan, the weight difference between male and female newborns was not statistically significant [13, 15]. These findings are not in line with WHO reports and several other studies that suggested that female newborns were at the risk of underweight [16, 17].
As the age increased, the gradient of this index increased more and more between boys and girls, insofar as in a relatively uniform manner at all times, the average weight of boys was higher than that of girls. This finding is consistent with the results of several other studies [18, 19, 20, 21]. It is important to note that in comparison of groups and populations, the reliance on the average index for comparative remarks is confronted with certain problems. Although the average weight of male infants in all periods has been higher than that of the girls, underweighted male infants in all stages of growth have been more than the female underweighted infants, and this shows the practical nature of frequency indicators compared to average based indices in population comparison.
While the rate gradient of changes in male underweighted infants was steeper in all points of the two years period as compared to female infants, the gradient of the changes in the average weight of the boys was the same in comparison to the girls in the whole follow-up period. Ayatollah et al., have studied the growth trend of 256 newborns and reported the highness of the growth rate of male infants as compared to female infants in the first year and the uniformity of growth rate from the first year onwards. In an alternative study the increasing trend in weight in ten days and thirty days was related to maleness [9, 19].
The average height for age of newborn infants showed a less than half a centimeter difference in the male newborns as compared to baby girls. In several other studies, the neonatal height of male newborns was reported to be higher than girls [14, 22, 23]. With the increase in the age of infants, this growth difference showed an increasing trend, insofar as from 1 month to 24 months, the height difference of 1 cm continued with male infants’ superiority over the female infants. Generally speaking, the boys' height increase as compared to girls is significantly different over the entire two-years period of suckling. The current finding is consistent with the results of other studies in the later stages of the development of children and adolescents, including a longitudinal study (cohort study) in a region of Korea on a group of children of 6 years old and up the average of this index was higher in boys than in girls to the ultimate height growth (173.5 and 160.5 cm respectively), which is consistent with the results of the cross-sectional study of 2007 in Korea [24, 25]. In all postnatal growth stages the average height of boys has been one cm more than that of girls. On the other hand, despite the fluctuation in the ratio of weight loss in different periods, in all courses, the ratio of underweighted male children was higher than that of the girls.
The average of head circumference for age at birth showed a slight difference in male newborns compared to the female newborns. This finding is consistent with the results of several other studies and this difference has been statistically significant in the study by Ali Malayeri et al. [14, 23, 26]. As the age of children increased, this growth difference showed an increasing trend, insofar as after the first month to one and half years, the difference in growth between male suckling infants as compared to the female ones continued with a stable height of 0.7 cm. Many other similar studies have also confirmed this finding [18, 19, 20, 21].
Generally speaking, despite the closeness of weight, height and head circumference difference between male and female newborn infants, their growth difference over the two-years period has recorded the superiority of boys. Some of the WHO standard growth charts show the difference between the two genders [18, 19, 20, 21]. But the noticeable point in this study is the persistence and stability of significant differences in the indicators discussed as regards boys compared to girls and the increase in the difference gradient from 9 months onwards. In Iran the mother are advised to use supplement nutrition from 4-6 months, and more than 90% of infants will benefit from supplement from about six months. This shows the correlation between the period of using supplement and the increase in the difference in growth rates. The similarity of temporal and spatial conditions provides researchers little justification for justifying the observed pattern. In other words, unsystematic attention to child nutrition, especially male infants, in the family, and even lack of attention to childhood care, can explain the wide range of changes and differences observed if they do not explain all the differences.
The findings of the current research showed that the prevalence of underweight for age at birth was nearly four percent in both sexes, and this ratio was almost the same for male and female newborns, which is consistent with the results of the Ayatollahi’s study that was conducted in Maku (3.9%), but it is inconsistent with the study that has been conducted by Ali Malayeri et al. both in frequency (9.3%) and in gender (male and female, respectively 10.9% and 7.7%). Moreover, according to the UNICEF 2013 report, this indicator is of 15 percent prevalence in the world in under 5 age group and reaches 25 percent in South Asian countries [6, 9, 14].
Although at the end of two years, the ratio of underweight for the whole sample under study remained almost constant, but this stability was not associated with maintaining the pattern of gender distribution at birth, insofar as the percentage of underweight in male sucklings is increased, but declined in female infants. If we are supposed to interpret these changes in line with the previous discussion, this seems to be due to the improvement in the height growth of male infants as compared to the weight gaining of these children in comparison to girls.
According to wasting index (underweight for height), in the early days of birth, minor wasting in male newborns was about four times higher than girls. Moreover, in view of moderate and severe weight loss (wasting), the prevalence of these degrees of underweight in boys was about one and a half times higher than female infants. This finding is consistent with the results of several other studies [19, 27], while the results of several other studies are contrary to this finding, e.g. in a study in the Gamb province of Nigeria, prevalence of weight loss was higher in girls as compared to boys (2.6 and 2), and severe wasting in both sexes was zero [21, 28].
The proportion of minor short stature at birth in male newborns was about one-and-a-half percent higher than girls. This index for severe stunting at birth was nearly equal in both genders. In other words, generally speaking, short stature in boys has been more prevalent than girls. This finding is consistent with some other studies, including the study that has been conducted by Zhank in Bangladesh. The prevalence of short stature at birth in boys (18%) was higher than girls (14%) [29, 30].
The trend ofchanges in minor and severe stunting in all the infants under study during the two-years period has shown an increasing trend. The point that is noteworthy in this observation is that the gradient of increase in boys has been more as compared to girls. To put it otherwise, severe stunting was more prevalent in boys with higher age, and striking height changes in infants continued to show greater resistance to this point. The prevalence of short stature in this study is consistent with the results of the Nigerian study (the prevalence of moderate short stature in males and females were respectively 47% and 33%, and severe short stature were 14% and 12% respectively) .
The prevalence of short stature in this study is consistent with the results of the Nigerian study (the prevalence of moderate stunting in male and female infants). However, since the index of stunting is more indicative of chronic malnutrition mainly due to micronutrient deficiencies, serious attention is needed to be paid to eliminating the effective factors such as socioeconomic, nutritional and environmental problems. In several studies, the main cause of short stature has been traced back to poverty, and in the next stages, to inattention, parasitic infections and genetic factors [31, 32]. In a study the positive and direct impact of consumption of the iron supplement has been shown to increase height lengths after 6 months .
The percentage of smaller head circumference at birth in both genders has been less than 1 percent, and this trend remained relatively constant during the course of the growth. To state the matter differently, the index showed a desirable status in the population under study. In a study, the direct effect of breastfeeding on the proper growth of the head has been shown . Although, no significant difference was seen at birth in the sextuple indexes (weight, height, head circumference, underweight, wasting and stunting) between boys and girls, and though the average weight, height, and head circumference indices were better in boys as compared to girls, but over a two-years period, the prevalence of underweight, wasting and short stature was higher in boys than in girls, and this is a remarkable point that is not consistent with presuppositions of of better male infants’ growth indices as compred to those of the female infants. To the state the matter in different words, against the existing expectations, the status of growth indices in boys is worse than those of girls, and this issue deserves to be taken into account in view of the justce in sexual health. The family structure in Iran, Iranian boys’ responsibilities in the family system, and finally the increased prevalence of these indicators in male group, double the necessity of adopting preventive approaches to children's nutritional care. It seems that the change in Iranian families general attitude as regards preferring to have girls instead of boys is one of the most important justifications for this difference in the growth trend. Another point that might be useful in justifying this finding is that, despite the attention that is paid by families to boys within the families of male newborns, the family's cultural, social and economic conditions are more effective than the parents' desire in infants growth. This is merely a theory that the present study does not provide strong evidence of its confirmation or rejection, and it requires a special study to be designed so as to clarify the position of the parents' desire to change versus the family's scientific ability to change their child's development. Moreover, the results of the current research serve as a warning to the effect that the emphasis on mental beliefs (a health justice gap with male gender superiority to the girl) need to be replaced with the approach of "analysis of justice in health based on evidences", so that as a result of mere attention based on theoretical foundations of policy makers, the opposite group (boys) do not suffer damages following the theoretization. We should not forget that two important goals (goals 3 and 4) of the 8th MDG2015 are child health and gender equality . Then, though the families need to increase their awareness and knowledge in order to change their attitudes, beliefs and practices, there is still a more urgent thing here, i.e. having clear evidences of the existence of a gap orthe superiority of a particular sexual group. by probable outliers, equality of variances, and the assumption of normal distribution of data, such as multivariate regression analysis, and so on and so forth.