A pre delivery enema was initially given in order to clean up the bowels completely before a woman gave birth. This was done especially to reduce the possibility of passing feces while the woman is in labor. It was thought that if the woman hasn’t had bowel movement before delivery, the contractions may cause the woman to inadvertently pass feces.
Later, pre delivery enemas began to be given in order to speed up the delivery of those women who have been in labor for a long time but haven’t been able to give birth. Both the practices have largely been given up now.