bwskel output have different spacing with the input labelmap 3d image

I am using bwskel to get the centerline of a label map 3d image. The dimensions of the label map image is 512,512,236 and the dimensions of the output image of bwskel are also the same. However, the spacing of the output image is 1,1,1 while the spacing of the original image is 0.5,0.5,0.75. Why does the bwskel change the spacing and how can I make it to generate the output with the same spacing as the input?

[Image Analyst]

Why do you say the spacing has changed when the array dimensions are the same. Please attach a small example of data in a .mat file, and code to demonstrate what you say.