Vitamin D deficiency in the system “mother – placenta – fetus”
Advances in perinatal medicine, which has been rapidly developing in recent decades, have led to a significant increase in the survival rate of premature babies with very low and extremely low birth weight. However, among preterm infants who have survived critical conditions, follow-up observation shows an increase in the proportion of disabling diseases, including delayed postnatal growth and neurological deficit. It is relevant to find unused reserves for the prevention of growth disorders, neuroprotection, neurorehabilitation and immunotherapy of perinatal brain lesions in premature infants. Such reserves include correction of vitamin D deficiency.
Vitamin D is a group of biologically active substances, the main of which are colecalciferol (vitamin D3) and ergocalciferol (vitamin D2). Vitamin D3 is synthesized in human skin under the influence of ultraviolet radiation, and can also come from food. Vitamin D2 can only come with food. Vitamin D is an important pre-hormone involved in many metabolic processes. Its deficiency has been recognized as a pandemic with many health consequences since the period of fetal development. Vitamin D deficiency has negative effects on human health and is defined as a public health problem in many countries. Newborns and premature babies are one of the most sensitive population groups for the development of vitamin D deficiency. Studies on the assessment of vitamin D availability in newborns are few, conducted mainly by foreign authors. The works of domestic authors who studied the effects of vitamin D deficiency in children were carried out in regions located in the central and northern parts of Russia (Moscow, St. Petersburg, Kazan, Arkhangelsk). In a study conducted in 2013–2015. in the Stavropol Territory, a high frequency of hypovitaminosis D among children from 0 to 3 years old was found that exceeds that in the central and northern regions of our country, which indicates an unreasonable reassessment of the value of the natural insolation factor in the synthesis of vitamin D in the autumn-winter period and significant reserves of drug prevention in the south of Russia .
Antenatal provision of the child with vitamin D
The availability of vitamin D of the fetus and the newborn depends on the content of vitamin D in the mother. The concentration of the main transport form of vitamin D – 25-hydroxycholecalciferol (25 (OH) D) in the umbilical cord blood of a child is 50–80% of the level of 25 (OH) D in his mother’s blood, regardless of gestational age. The widespread prevalence of vitamin D deficiency among pregnant women also explains the high level of vitamin D deficiency in newborns and children in the first months of life.
The frequency of hypovitaminosis D in pregnant women and newborns varies in different countries depending on race, lifestyle, feeding, season and vitamin D intake during pregnancy. Thus, a level of 25 (OH) D in the blood of less than 20 ng / ml was observed in 18% of non-Hispanic white mothers in the USA, in 42–48% of pregnant women in Canada, Australia and the UK, in 68–82% of pregnant women in Finland, India, New Zealand, as well as African American mothers in the United States, 98% of women in the UAE [. According to several studies, vitamin D deficiency with a concentration of 25 (OH) D in the blood of less than 10 ng / ml was observed in 15% of newborns in Denmark, 51–64% in Iran, Turkey and Ireland, and with a concentration of less than 20 ng / ml – in 61–64% of newborns in the USA and Denmark, in 83–92% – in India, Ireland and Turkey. Moreover, in all studies, a significant improvement in the vitamin D status of pregnant women and newborns was noted if the woman received a vitamin D subsidy during pregnancy.
There is currently no consensus on the optimal blood 25 (OH) D content in newborns and premature babies. Vitamin D levels in these categories of children are compared with data from adults. According to the results of a study conducted by the Federal State Budgetary Institution Scientific Research Center for Medical Sciences named after IN AND. Kulakova ”of the Ministry of Health of the Russian Federation in 2015–2016, most children, regardless of gestational age, are born with insufficient levels of vitamin D. Medians of 25 (OH) D values in the blood in the first week of life did not reach 15 ng / ml, in 85% neonatal level 25 (OH) D was lower
20 ng / ml, and in 1/3 of children – below 10 ng / ml. In preterm infants, during the first year of life, the lowest level of 25 (OH) D was detected in winter and the highest in summer: 8.1 ng / ml (3.3-14.5) versus
17.9 ng / ml (4.5–29.3), p <0.05. Among the risk factors for vitamin D deficiency in premature babies, one should consider maternal vitamin D deficiency, prolonged parenteral nutrition, suboptimal nutrition, treatment with barbiturates, cholestasis syndromes and malabsorption.