Meconium stooling is seen in 90 percent of newborns within the first 24 hours, and most of the rest within 36 hours. The passage of meconium and urine indicates patency of the gastrointestinal and urinary tracts. Failure of the newborn to stool or urinate after these times suggests a congenital defect, such as imperforate anus or a urethral valve. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 28. The Newborn Infant. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.