**2. Value of selenium deficiency in the perinatal period**

Adequate provision of selenium for pregnant women, premature infants, children of different ages, and adolescents living in environmentally unfavorable conditions and constituting a risk group for selenium deficiency is particularly relevant [2–7].

Nefedova et al. [8] believe that the fact of selenodetic in healthy women in Western Siberia is associated with the possible formation of "anomalous biogeochemical province" endemic selenium. In pregnancy, even with the physiological course, this deficit is exacerbated, which is an understandable increased expenditure of trace elements [9–11]. In women at risk of termination of pregnancy, selenium deficiency is most pronounced, with pregnancy ending in miscarriage at different stages [12–15].

The level of selenium (serum, erythrocytes, urine, and hair) in healthy adult blood donors, residents of Khabarovsk in the preconception (indicator group), at the end of physiological pregnancy (group "healthy pregnant") and breast milk on the 7–10 day after birth in mothers of healthy newborns and preterm infants was established.

There were no differences in the content of selenium in the serum of young healthy nonpregnant women, donor volunteers (residents of Khabarovsk, examined by random sampling), healthy pregnant women at the end of physiological pregnancy, and healthy puerperas. The provision in these groups was found to be average (82–85 μg/l), which is approximately 80% of the optimal level, since the interval of normal serum concentrations of selenium is on average 115 μg/l. At the end of physiological pregnancy and normal childbirth, the level of selenium in the blood serum was determined within 85.4 + 4.8 μg/l and 82.6 + 6.1, respectively, which is lower than optimal for pregnant women. In premature births, serum levels of selenium were significantly lower—58.2 μg/l, which is about half of the optimum. There are no significant differences in the content of selenium in the blood inversion in smoking and nonsmoking women in the indicator group (82.8 + 16.2 and 83.1 + 15.9 μg/l) or in the group of healthy pregnant women (84.7 + 15.8 and 85.8 + 16.1 μg/l), in the presence of significant differences in the hair of smoking and nonsmoking pregnant women (383.0 + 24.4 and 436.6 + 28.2 μg/l, respectively, p < 0.01).

During pregnancy, there is a significant reduction in the excretion of selenium in the urine, which ensures the maximum possible provision of the fetus with a trace element [16]. Excretion of selenium in urine is constant and is normally 40–50% of intake [17]. Losses of selenium with urine in the group of healthy pregnant women in Khabarovsk ranged from 12.6 to 40.8 μg/l, on average 23, 68 μg/l, which differs with a high degree of reliability from the standards described in the literature.

A direct relationship of average strength between the level of selenium in the hair and urine of pregnant women indicate unidirectional changes in the concentration of selenium in the hair and urine of pregnant women.

Also in the process of gestation, there is a change in the content of selenium in serum and in hair, and there is a highly reliable feedback of average strength between the content of selenium in serum and hair of pregnant women.

In young healthy nonpregnant women, the existence of a direct relationship of moderate strength (r = 0.4804) is established between selenium content in blood plasma and urine, and there is a highly significant direct strong correlation between selenium in serum and erythrocytes (r = 0.9552), direct medium strength correlation between selenium in urine and selenium in erythrocytes (r = 0.4348). At the same time, during the physiological course of the gestational process in healthy mothers, serum selenium levels and urine selenium values have a direct relationship of average strength.

The loss of selenium in urine was significantly lower (p < 0.05) in women with a long labor period (18.6 + 0.76 μg/l) and higher in mothers with planned operative labor (24.9 + 1.3 μg/l), and there was no dependence on the gestation period. Probably, the detected changes are associated with the development of oxidant stress; since the intensive physical activity (childbirth) determines the acceleration of metabolic processes, leading to significant oxidant stress of the body, a specific mechanism is included that ensures the preservation of selenium by reducing its excretion in the urine [18].

On the territory of the Khabarovsk, there is a shortage of selenium, because in the food diet of the inhabitants of the region, local products prevail, including from

#### *The Importance of Selenium in Children's Health and Reproduction DOI: http://dx.doi.org/10.5772/intechopen.88864*

household plots, which, in conditions of natural low maintenance, contain little of this element. The problem is also aggravated by the fact that our study of the diet of young children showed a significant deficit in the consumption of the surveyed residents of Khabarovsk products—sources of selenium, which undoubtedly exacerbates the population deficit.

In the epidemiological study of the provision of selenium in children permanently living in Khabarovsk, we have established a significant variability in the provision of selenium in different age groups of children with maximum security in adolescents 12–17 years; the minimum level of selenium was detected in children aged 2 years of life, due to the peculiarities of nutrition and food preferences of children of different ages. In general, selenium deficiency was observed in 18% of the surveyed children; only 28% of children found trace element content at the lower limit of the norm. The data obtained by us on the provision of selenium for children and residents of Khabarovsk are comparable with the data obtained by us from the adult population [19].
