Placental gross / microscopic abnormalities, nonneoplastic
Meconium staining

Author: Mandolin Ziadie, M.D. (see Authors page)

Revised: 13 October 2017, last major update October 2011

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Meconium staining placenta

Cite this page: Ziadie, M. Meconium staining. website. Accessed October 16th, 2018.
  • Passage of meconium in utero is due to bowel peristalsis and relaxation of anal sphincter and may be indicative of fetal distress
  • Meconium components diffuse into placenta and cord, leading to vasoconstriction and hypoperfusion; damage to fetus increases with length of exposure
  • Neonates are at risk for meconium aspiration
  • Meconium is unlikely in fetuses prior to 30 weeks gestation
Gross description
  • Green brown discoloration of the cord, fetal surface and membranes: differentiate between deposition of slimy green meconium across placental surface that is washed off with a gentle rinse (normal fetus that passes meconium shortly after delivery) and true mecomium staining (exposure to meconium for several hours)
  • Membranes may be edematous or slimy
Gross images

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Green black meconium

Microscopic (histologic) description
  • Vacuolation of the amnionic epithelium, edema of the soft tissue plane between the amnion and chorion and pigment laden macrophages within the amnion and chorion
  • Prior to 34 weeks, pigment in the membranes is usually hemosiderin
  • When prolonged, exposure to meconium can lead to necrosis of individual myocytes in the umbilical and chorionic plate vessels (meconium induced vascular necrosis); this finding increases the risk of neurologic sequelae
  • Mild: superficial necrotic or sloughed amniotic epithelium with meconium containing macrophages confined to the surface
  • Moderate: ballooning of vacuolated amniotic epithelium with obvious meconium containing macrophages adjacent to chorionic tissue; indicates meconium discharge at least 2 - 3 hours before delivery
  • Severe: moderate histologic findings but with more macrophages; may have meconium induced necrosis of umbilical vessels with myocyte necrosis; indicates fetal meconium discharge 6 - 12 hours before delivery
  • Associated chorioamnionitis may be present but is not caused by meconium
Microscopic (histologic) images

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