Vitamin D deficiency is a global public health problem as mentioned by Cardoso Do Prado MRM et al. due to its high prevalence of it; in Mexico, it is also a common problem since it has been reported that 62% of mothers have VitD deficiency (< 20 ng/ml) at 4 weeks postpartum. 1, 27 Although there are few studies evaluating vitamin D deficiency in the mother and her newborn, our study agrees with worldwide results with insufficient/deficient levels of VitD in 89.7% of newborns and 75.8% of mothers studied. It is noteworthy that 98.4% of mothers received multivitamins during pregnancy, however, none received vitamin D supplementation due to prescribed formulations.
Obese patients have been reported to have lower concentrations of 25 (OH) VitD 28, 29, however, there are no studies in medical research that evaluate the correlation between maternal obesity and vitamin D levels in newborns, which was one of our objectives, despite this, we found no significant correlation between neonatal VitD deficiency and maternal obesity. In Mexico, Elizondo et al. determined the prevalence of vitamin D deficiency and the association between obesity and lifestyle in school patients and reported an insufficiency of 62% and a deficiency of 20.2% 30, however, their cut-off point for insufficiency was higher than in our study (21–29 ng/ml) therefore we could underestimate the insufficiency/deficiency of maternal-fetal VitD with the cut-off point used.
During the last trimester of pregnancy, the product receives the greatest contribution of maternal minerals, that’s why premature infants have low reserves of these minerals that, together with their low weight and associated comorbidities, increase the risk of mineral insufficiency and alterations in bone metabolism, which is demonstrated in our study by having insufficiency/deficiency in 89.7% of newborns with gestational ages between 30–41 GW, which has an impact on the morbidity and mortality of preterm infants.
Limitations of our study included the number of patients included, which could be the guideline for experimental designs with larger population samples.
Although international guidelines recommend supplementing VitD to premature infants, in our country we do not have the required dose presentation. Similarly, the majority of VitD deficient/insufficient pregnant mothers consumed multivitamins during pregnancy, without Vitamin D included, which is required in a dose of 2000–5000 IU depending on the level of deficiency. 15, 24, 25, 26
There is a close association between circulating levels of vitamin D in the mother and the fetus, so maternal deficiency is reflected in the newborns as we demonstrated in the study.
Studies that correlate maternal weight and BMI with neonatal vitamin D levels are not described in the literature, so we decided to study them. However, no correlation was found.
Vitamin D deficiency in adults has been associated with the use of sunscreens, as well as with the lifestyle in which most people work and that involves low sun exposure, that’s why researching these other determinants in women pregnant women would be a proposal for future studies. Since another factor is poor diet, we recommend pregnant women to have a balanced and complete control of their diet, which would also prevent overweight/obesity, which was found in 59 (93.6%) of mothers in our study.
An objective in future studies is to expand the sample with more premature newborns and correlate with comorbidities, type of ventilation, and diseases (not only in the neonatal period but also in childhood) to investigate alterations in minerals (Calcium and phosphorus) and diseases of bone metabolism.
Vitamin D levels in human milk are 5U/liter and given that term infants should receive at least 400U daily and premature infants between 800-1000U, children under one year exclusively breastfed need vitamin D supplementation, also those who are weaned and consume less than one liter of formula per day15, 24, 25, 26.