Placental meconium

Placental meconium, also known as meconium staining, is associated with fetal distress.

Placental meconium
Diagnosis in short
Meconium-laden macrophages. H&E stain.
LM	macrophages with brown fine granular pigment in the amnion +/- chorion
LM DDx	hemorrhage
Stains	PASD +ve, Prussian blue -ve
Gross	green discolourization of fetal membranes
Site	placental membranes
Associated Dx	+/-chorioamnionitis
Clinical history	+/-non-reassuring fetal heart rate
Prevalence	uncommon
Prognosis	benign

General

• Associated with fetal distress.
• Small amount - at term - is considered to be normal.

Other meconium-related pathology:

• Meconium peritonitis.
• Meconium ileus.

Gross

• Fetal membranes with a green discolourization.

Microscopic

Features:

• Meconium histiocytes - key feature.
  • Macrophages with brown fine granular pigment.
• Pseudostratified epithelium (amnion) - low power.
• Amnion - columnar morphology (normally cuboidal).
• "Drop-out" of individual amnion cells / loss of individual cells.

Time of meconium passage:

• <1 h - no staining of membranes.
• 1-3 h - amnion is stained.
• >3 h - chorion is stained.

DDx:

• Hemosiderin-laden macrophages.
  • This is sorted-out with an iron stain -- see below.
• Chorioamnionitis - apoptotic cells may be mistaken for neutrophils.

Notes:

• The above time course is disputed - in vitro experiments suggest it is considerably longer.

Images

• 

  Meconium-laden macrophages - high mag. (WC)

• 

  Meconium-laden macrophages - intermed. mag. (WC)

Special stains

• Hemosiderin +ve in hemosiderin-laden macrophages.
• PAS +ve in meconium-laden macrophages.

Useful to differentiate hemosiderin-laden macrophages and meconium laden macrophages:

• Hemosiderin stain -- +ve for old blood.
  • Prussian-blue stain = hemosiderin stain.

Notes:

• PAS-D -- +ve in meconium... though may rarely stain hemosiderin.
• Meconium contains bile.

Sign out

PLACENTA, UMBILICAL CORD AND FETAL MEMBRANES, BIRTH:
- FETAL MEMBRANES WITH MECONIUM-LADEN MACROPHAGES, NEGATIVE FOR CHORIOAMNIONITIS.
- THREE VESSEL UMBILICAL CORD WITHIN NORMAL LIMITS.
- PLACENTAL DISC WITH THIRD TRIMESTER VILLI WITHIN NORMAL LIMITS.

COMMENT:
A PAS-D stain and Prussian blue stain were used to confirm the presence of meconium.

Degenerative changes present

PLACENTA, UMBILICAL CORD AND FETAL MEMBRANES, BIRTH:
- FETAL MEMBRANES WITH MECONIUM-LADEN MACROPHAGES AND DEGENERATIVE CHANGES, 
  NEGATIVE FOR CHORIOAMNIONITIS.
- THREE VESSEL UMBILICAL CORD WITHIN NORMAL LIMITS.
- PLACENTAL DISC WITH THIRD TRIMESTER VILLI WITHIN NORMAL LIMITS.

Not definite

PLACENTA, UMBILICAL CORD AND FETAL MEMBRANES, BIRTH:
- EARLY CHORIOAMNIONITIS.
- FETAL MEMBRANES WITH FOCAL AMNION CELL DROP-OUT AND RARE PIGMENTED
  CELLS SUGGESTIVE OF MECONIUM.
- THREE VESSEL UMBILICAL CORD WITHIN NORMAL LIMITS.
- PLACENTAL DISC WITH THIRD TRIMESTER VILLI.

See also

• Placenta.
• Chorioamnionitis.
• Meconium peritonitis.
• Meconium ileus.