Biochemical analysis  
Despite the challenging and ongoing discussions on how to measure the level of vitamin D current guidelines recommend measurement of 25(OH)D (1). The maternal and umbilical cord blood were sent directly to the hospital’s central laboratory for analysis by an electrochemiluminescence binding assay using Liaison 25-hydroxy-vitamin D TOTAL. The laboratory is internationally certified by Analytics Professional (CAP) and has accreditation from The International Organization for Standardization (ISO). The cord blood gases and electrolytes were analyzed directly on the labor ward by stationary blood gas analyzer (ABL90, Radiometer, Copenhagen, Denmark).