Any measurement in which the number of individuals in a study population that display meconium ileuss at a point in time or develop meconium ileus within a determined period of time are compared to the total number of individuals in the study population. Often expressed as a percentage but could be expressed as a ratio. Meconium ileus is intestinal obstruction due to inspissated meconium in the distal ileum and cecum, which develops in utero and presents shortly after birth as a failure to pass meconium.