How is it that Pilate has no navel

From the text:

After their mother died, she had come struggling out of the womb without help from throbbing muscles or the pressure of swift womb water. As a result, for all the years he knew her, her stomach was as smooth and sturdy as her back, at no place interrupted by a navel. It was the absence of a navel that convinced people that she had not come into this world through normal channels; had never lain, floated, or grown in some warm and liquid place connected by a tissue-thin tube to a reliable source of human nourishment.