Relationship between vitamin d levels, maternal vitamin Dlevels, vitamin D gene polymorphism, and respiratory distress causes in patients receiving respiratory distress treatment in neonatal intensive care unit

The main source for the Vitamin D is its synthesis in the skin on exposure to sunlight. Vitamin D protects against certain diseases during pregnancy, early childhood and the other periods of life. The serum 25 (OH) vitamin D level in cord blood is 50%–60% of the mother's serum level. Therefore, mothers' low serum vitamin D levels are considered as the most significant risk factor for vitamin D deficiency or insufficiency in early infancy. Serum 1.25 (OH) 2 vitamin D is the most active form of vitamin D, and it exhibits its effect via vitamin D receptor (VDR) on target tissues. Many tissues contain VDR, and this receptor gene has various polymorphic forms in humans. Fok I, Bsm I, Apa I, and Taq I are the most-defined long-fragmented polymorphisms. Although vitamin D has been investigated in terms of its effect on cardiovascular, immune, respiratory, and many other systems besides calcium and bone metabolism, studies on its effect on the mother and the baby during and after pregnancy are ongoing. This study aimed to determine the serum 25 (OH) vitamin D level and gene polymorphisms (Fok I and Taq I) in the neonates and the relationship between respiratory diseases and respiratory morbidities. Materials and Methods: The patient group comprised 67 newborns at 34–42 weeks gestation admitted to Bülent Ecevit University Medical Faculty Hospital Neonatal Intensive Care Unit between March and August 2018 due to respiratory distress, and their mothers. The control group consisted of 67 healthy newborns at 34–42 weeks gestation (GH) and their mothers. Demographic characteristics, birth week, birth weight, type of delivery, cause of premature birth, probable intervention at birth, prenatal information, single/multiple pregnancy status, antenatal steroid application status, routine drugs used by the mother during pregnancy, causes of respiratory distress of all cases, and the presence of conditions such as transient tachypnea of the newborn (TTN), respiratory distress syndrome (RDS), congenital pneumonia, bronchopulmonary dysplasia (BPD), surfactant application status, additional complication, meconium aspiration syndrome, air-leakage syndromes, and pneumothorax were investigated. A questionnaire was administered to all mothers in the patient and control groups after obtaining their informed consent. Age, educational status, drugs used during pregnancy, usage of sunscreen and multivitamin, headscarf usage, and type of residence were also investigated. Results: 50.8% (n = 68) of the newborns in the patient and control groups were female and 49.2% (n = 66) were male (p > 0.05). The gestational week averages were 36.0 ± 1.6 weeks in the patient group and 36.9 ± 1.4 weeks in the control group (p > 0.05). The mean birth weight of the newborns in the patient and control groups was 2774.8 ± 563 g and 2828.0 ± 550 g, respectively (p > 0.05). The mean vitamin D level of the newborns in the patient and control groups was 15.8 ± 8.8 ng/mL and 17.2 ± 6.6 ng/mL, respectively (p > 0.05). The mean vitamin D level of the mothers in the patient and control groups was 13.01 ± 7.7 ng/mL and 16.6 ± 7.2 ng/mL, respectively (p > 0.05). The relationship between vitamin D levels and respiratory morbidities of newborns was investigated. No statistically significant relationship among RDS, TTN, congenital pneumonia, and vitamin D levels of newborns admitted to the neonatal intensive care unit was found (p > 0.05). The genetic evaluation was performed in newborns and controls. In the genetic evaluation stages, two newborns from the control group were excluded from the study due to the lack of DNA isolation. As a result, a total of 132 newborns (67 in patient and 65 in control group) were included in the genetic evaluation in this study. The ff genotype of VDR Fok I polymorphism was not detected in this study group. No statistically significant difference in FF and Ff genotypes of VDR Fok I polymorphisms was found between the patient and control groups (p > 0.05). VDR Taq I polymorphism was studied with 67 neonatal patients in the patient group and 65 neonates in the control group. No statistically significant difference in CC, CT, and TT genotypes of VDR Taq I polymorphisms was found between the patient and control groups (p > 0.05). No relationship between vitamin D levels and the gene polymorphism of neonates was found in this study (p > 0.05). The relationship of VDR Taq I and Fok I polymorphisms with respiratory morbidity in newborns was investigated. No statistically significant relationship was found between both gene polymorphisms, and RDS, congenital pneumonia and TTN (p > 0.05). Discussion and Conclusion: Vitamin D deficiency in women of fertility age has been reported to be 80% in Turkey. No statistically significant relationship was found between the maternal and neonatal vitamin D levels and neonatal respiratory morbidity in the present study. No significant relationship was found between Fok I and Taq I gene polymorphisms and respiratory morbidities in terms of genetic polymorphisms. Future studies with larger populations would allow a clearer understanding of the role of VDR gene polymorphisms in the pathogenesis of respiratory system diseases and many other systemic diseases. Moreover, the vitamin D support provided within the scope of health ministry support program can be applied more effectively with more frequent follow-up of pregnant women. In addition, the problems that might occur due to vitamin D deficiency in the postpartum period of mothers and neonates can be reduced.