Failure to pass meconium within 48 hrs of birth in a newborn with no obvious external abnormality should lead to the suspicion of –

Read what Nelson says about Hirschsprung's disease (Congenital aganglionosis). "Ninety-nine per cent of full-term infants pass meconium within 48hrs of birth. Hirschsprung disease should be suspected in any fill term infant with delayed passage of stool".