In the present study, we evaluated level of serum vitamin D and the different range of it in both neonates and mothers. More than 50% of mothers and infants were in sufficient group.
Prevalence of vitamin D deficiency is high in developing countries as well as its resurgence in developed countries. It is related to several lifestyles and environmental factors such as insufficient exposure to sunlight, increased breastfeeding among women with dark skin, and declining numbers of doctors typically feeding vitamin D supplements to infants (13, 14).
Classically, nutritional rickets presents after 6 month of age. According to two studies with a relatively high patient population, the youngest patients were 5 and 4 months old and the mean age at diagnosis was 14.6 and 20.2 months, respectively (15–19).
Exclusively breastfed infants according to recent guidelines from the American Academy of Pediatrics should intake at least 5 micrograms of vitamin D for at least the first 2 months. In addition, they recommend vitamin D supplementation to all infants (20).
According to one study deficient infants combined high-dose maternal vitamin D3 supplementation (2000 IU once daily or 60 000 IU once monthly) and 400 IU once daily. So that vitamin D status improve significantly (8).
Most of the neonates of our study born in autumn and winter. These seasons have inadequate sunshine and people intake less vitamin D. We found that there is not any significant relation between vitamin D level of mothers and neonates and season of birth. The importance of sunshine discussed in previous other reports (5, 21).
The correlation between the level of vitamin D in infants and mothers is not significant. As long as the growth rate is high in the first 2 years, supplementation should be recommended for all children under 2 years of age. Similarly, adolescence is also a period of fast growth (22).
Un-supplemented infants had low serum 25(OH) D3 levels, particularly if exclusively breast-fed and during winter (23, 24).
In addition, significant relationship was not shown between gender and vitamin D and the mean level in boys was higher than girls.
Clara Crescioli et al showed that there are some factors that is affecting vitamin D action which name is gender-dependent factors. There is sex-related differences of "absolute" vitamin D levels so these factors seems to be critical (25).
Other variables in our study for instance gestational age and age of neonates were not correlated with vitamin D. But other significant correlation was between vitamin D and head circumference reversely; and also age of mothers directly.
Low 25-hydroxyvitamin D3 (25(OH) vitamin D) or calcidiol, levels according to Different studies have some relation with low birth weight and gestational age (26).
High dose vitamin D supplementation have some beneficial and adverse outcomes during pregnancy. A large randomized controlled trial in 2004 showed maternal and fetal outcomes with supplementation high dose vitamin D (4000 IU/day) starting before 16 weeks’ gestation. Either in the mother or the fetus, they didn’t reach to any association with adverse events at this dose (27).
There appear to be fewer pregnancy-associated comorbidities with serum vitamin D concentrations > 40 ng/ml (28) highlighting the importance of achieving adequate serum concentrations of vitamin D.
Vitamin D3 supplementation according to Doria K Thiele et al study is an effective intervention from prenatal to postpartum. This supplementation can increase status of vitamin D in mothers and promote this status in exclusively breastfed infants and newborns (29).
The neonatal vitD status at birth and at two weeks of age had a strong, direct and significant relationship with maternal vitD at the time of delivery, but the neonatal P, Ca and Alk level had a direct and significant correlation with maternal P, Ca and Alk level only at the time of birth, and unlike vitD, this relationship decreased significantly after two weeks (30).
During childhood and adulthood, vitamin D is an important element of bone health. Recently, studies showed that vitamin D develop other non-skeletal diseases which is important to improve the proper condition of vitamin D. Vitamin D supplementation should be recommended in all infants independently of the type of diet and should subsequently be individualized in terms of regimen and duration based on the presence of risk factors for vitamin D deficiency (22).
This study has limitations that need to be considered when interpreting results. We conducted a single-center observational study, and thus, as with any observational study, the potential remains for residual confounding.