46. The association of umbilical cord blood vitamin D level with children’s arterial stiffness at 7 years of age – HAPO follow up study

Introduction We recently reported the effect in utero exposure to maternal hyperglycaemia on children’s risk of abnormal glucose tolerance, obesity and higher blood pressure (BP) at 7 years of age among 962 offspring from the Hyperglycemia and Adverse Pregnancy Outcome study (HAPO) study. Objective To investigate the association of maternal and umbilical cord vitamin D deficiency with children’s cardiometabolic risk at 7 years of age. Methods Mothers who had joined the HAPO study, along with their children were assessed 7 years post-delivery for cardio-metabolic risk, which included carotid-femoral pulse wave velocity (cf-PWV). We performed interim analysis after 566 maternal serum at mid-gestation and 673 umbilical cord serum were analyzed for total vitamin D (25-OHD) levels using a liquid chromatography tandem mass spectrometry method which separates the biological inactive 3-epi-25(OH) D3 from 25(OH) D3, an isomer commonly present in infants. Results The mean maternal and umbilical cord 25-OHD levels were 58.52 ± 20.68 nmol/L and 41.06 ± 15.04 nmol/L respectively; 38.3% mothers had level below 50 nmol/l (vitamin D deficient). Maternal and umbilical cord 25-OHD significantly varied with the seasons. Umbilical cord, but not maternal, vitamin D level was negatively associated with children’s cf-PWV (unstandardized coefficients = −0.005, p = 0.003), independent of maternal glucose level at pregnancy, maternal hypertensive status at follow-up and other confounders, such as children’s age, sex & height. The association remained significant even adjusting for children’s BP (unstandardized coefficients = −0.004, p = 0.006). Discussion The result suggests that in utero vitamin D deficiency may be an independent factor for children’s future vascular risk. Further study is required to explore the association with the children’s Vitamin D status and the underlying mechanism.