The correlation between insulin resistance in preterm newborns who are small for gestational age and serum vitamin D levels of mothers and infants

Being small for gestational age (SGA) and the early postnatal catch up growth that cause an abnormal increase in adipose tissue are the two most important factors of insulin resistance that are seen in adulthood. Vitamin D deficiency is effective in varying degrees on the development process of glucose intolerance, diabetes mellitus (DM) and deterioration in pancreatic beta cell function or decrease in insulin sensitivity. In this study, we aimed to discuss the correlation between the serum vitamin D levels of preterm SGA newborns and their mothers', and the insulin resistance in these infants which could effect them during childhood and adult life. The study group consisted of 25 preterm SGA newborns admitted to our neonatal intensive care unite and their mothers, and the control group consisted of 25 preterm AGA newborns and their mothers who were specifically matched by gestational age. In the study a total of 50 newborns and their mothers were evaluated. The birth weight and height were significantly lower in the study group than the control group (p=0.001 and p=0.001). There were no statistically significant difference in gestational age, sex, type of delivery, head circumference at birth, 1st and 5th minute APGAR scores or antenatal steroid administration between the two groups (p>0.05). Body weight and height were significantly lower in study groups compared to control group during the 6th month examination (p=0.046 and p=0.022). However there were no significant difference in head circumference, feeding types and weight gain between the groups (p>0.05). While the frequency of preeclampsia, chronic hypertension, placental insufficiency and EMR were significantly higher in study group mothers than the control group (p=0.002), there were no statistically significant differences in age, gravidity, parity, weight gain during pregnancy, chorioamnionitis, smoking, urinary tract infection, and antibiotic usage between the two groups (p>0.05). Serum calcium, phosphor, magnesium, ALP, PTH and 25(OH)D3 levels were not significantly different between the mothers in the study and control group (p>0.05). Eighty percent of the mothers in the study group and 72% percent of the mothers in the control group had vitamin D insufficiency (<15 ng/ml). There was no statistically significant difference according to the ranges of serum 25(OH)D3 levels between the groups (p>0.05). Serum glucose levels of the newborns on day 2 were significantly lower in the study group than the control group (p=0.016), though there were no statistically significant differences in serum insulin, calcium, phosphor, magnesium, ALP, PTH, 25(OH)D3 levels and HOMA-IR values (p>0.05). There was a statistically significant positive correlation between mothers serum 25(OH)D3 levels and serum 25(OH)D3 levels of newborns on day 2 (r=0.42, p=0.002). There were no statistically significant differences in serum glucose, insulin, calcium, phosphor, magnesium, ALP, PTH, 25(OH)D3 levels and HOMA-IR values between infants in control and study group at 6 months of age (p>0.05). In our study, there was a statistically significant negative correlation between the serum 25(OH)D3 levels of newborns on day 2 and serum LDL cholesterol levels at 6 months of age (r= 0.34, p=0.005). In our study, we didn't find any correlation between the serum 25(OH)D3 levels of preterm SGA newborns and their mothers and the measurements of insulin resistance in these infants at 6 months of age. Besides, the glucose metabolism of preterm SGA infant who did not achieve early catch up growth in the first 6 months of life was not significantly different from AGA newborns. Key Words: Small for gestational age, prematurity, vitamin D, insulin resistance