Evaluation Of Serum 25-hydroxyvitamin D Level And Investigation Of Influencing Factors In Very Preterm Infants At 4 Weeks Of Age

Objective:To evaluate the status of vitamin D by measuring the serum level of 25（OH）D at 4 weeks of age in very preterm infants during hospitalization,and to explore the risk factors affecting vitamin D level,so as to provide evidence for clinical rational supplementation of vitamin D and reduction of vitamin D deficiency.Methods:A total of 158 very preterm infants with gestational age between 28 weeks and 32 weeks and admitted to hospital within 24 hours after birth and whose mothers with regular antenatal examintation were enrolled in neonatal intensive care unit of Qingdao Women and Children’s Hospital from January 2020 to October 2021.Infants with severe congenital malformation,whose mother had long duration of drugs usage which can affect bone metabolism during pregnancy,with positive family history of congenital osteogenesis imperfecta,to give up treatment,data incomplete were ruled out.During hospitalization,nutritional support was carried out according to the Clinical application guidelines of Neonatal nutritional support in China.During parenteral nutrition,electrolytes such as calcium and phosphorus,water-soluble vitamins and fat-soluble vitamins were supplemented through central veins.A dosage of 900 IU Vitamin D₃was orally supplemented daily at the age of 1～2 weeks postnatal under the condition of feeding tolerance.One milliliter of venous blood was taken at the age of 4 weeks after birth to measure the level of serum 25（OH）D.According to the results of serum 25（OH）D,the infants with 25（OH）D≥30 ng/m L were included in sufficient group（n=72）;25（OH）D<30 ng/m L were included in insufficient group（n=86）.The clinical data of the two groups were statistically analyzed by SPSS software.Results:1.Demographic characteristics:A total of 158 very preterm infants were enrolled,whoes gestational age were 28～31.9 weeks[30.0（29.0,30.9）]weeks and birth weight were800.00 g～2060.00 g（1368.90±245.71）g;There were 90 male patients（57.0%）and 68female patients（43.0%）,123 cases（77.8%）were singletons,35 cases（22.2%）were multiplets;95 cases（60.1%）were cesarean section and 63 cases（39.9%）were vaginal delivery.2.Serum level of 25（OH）D at 4 weeks postnatal in very preterm infants:The serum 25（OH）D level of 158 very preterm infants at 4 weeks of age was 13.63～52.38ng/m L,with a median level of 29.32（23.75,34.81）ng/m L.In sufficient group,72 cases（45.6%）had serum 25（OH）D level≥30 ng/m L;in insufficient group,there were 67cases（42.4%）with serum 25（OH）D ranging from 20 to 30 ng/m L,and 19 cases（12.0%）with serum 25（OH）D level<20 ng/m L.3.Serum levels of calcium,phosphorus and alkaline phosphatase in very preterm infants at 1～4 weeks postnatal:There were no significant differences in the serum levels of calcium,phosphorus and alkaline phosphatase between the two groups at1～4 weeks after birth（P>0.05）.4.Influencing factors of 25（OH）D level in very preterm infants at 4 weeks of age:There were no significant differences in gestational age,birth weight,sex,multiple births,delivery mode,Apgar score of 1 minute and 5 minute,maternal age,prenatal glucocorticoid application,maternal pregnancy hypertension incidence between the two groups（P>0.05）.There were no significant differences in the rate and duration of invasive mechanical ventilation between the two groups（P>0.05）.There were no significant differences in the feeding mode,the time of oral vitamin D supplementation before testing the serum level of 25（OH）D,the avergae dose of vitamin D supplementation per day via parenteral nutrition between the two groups（P>0.05）.The birth season of very preterm infants were different between the two groups.In the insufficient group,more very preterm infants were born in winter and spring（55.8%vs26.4%,X²=13.893,P=0.000）.The incidence of gestational diabetes mellitus in the insufficient group was higher than that in the sufficient group（39.5%vs 20.8%,X²=6.406,P=0.011）.The days of intravenous vitamin D supplementation via parental nutrition before testing serum level of 25（OH）D were longer in sufficient group than that in insufficient group[26.5（22.3,30.8）days vs 24.0（17.0,29.3）days,Z=-2.114,P=0.034].Multivariate analysis showed that winter and spring birth（OR=4.02,95%CI:1.92～8.41,P=0.000）and maternal gestational diabetes mellitus（OR=2.72,95%CI:1.26～5.89,P=0.011）were independent risk factors affecting the serum level of 25（OH）D at 4 weeks of age for very preterm infants.Conclusions:1.There is a relatively high incidence rate of vitamin D deficiency in very preterm infants at 4 weeks of age,and supplementation with vitamin D should begin as early as possible after birth.2.For very preterm infants with risk factors for vitamin D deficiency,such as born in winter and spring,whose mothers with gestational diabetes,vitamin D level should be monitored regularly and individualized vitamin D supplementation should be performed.