Placenta

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Author: Mikael Häggström [notes 1]

Comprehensiveness

On this resource, the following formatting is used for comprehensiveness:

  • Minimal depth
  • (Moderate depth)
  • ((Comprehensive))

Gross processing

  • Determine the shape of the placenta
  • Look for any accessory lobes
  • Determine the completeness of placental membranes, opacity, color and consistency (slimy/slippery?)
  • Determine the point of rupture from nearest margin
  • Note where the membranes are inserted
  • Examine the umbilical cord
  • Measure the distance between the insertion point and the nearest placental margin
  • Measure the cord length and give proximal and distal diameter. In placental pathology, the proximal umbilical cord refers to the segment closest to the placenta, and distal is the segment closest to the fetus.[notes 2]
  • Count the number of vessels away from the insertion
  • Weigh the trimmed disk, after having trimmed away the cord and membranes, and after having removed excess amounts of loose retroplacental blood clots over the maternal surface.
  • Examine the fetal surface (chorionic plate):
  • Note its color
  • Look for any pathologies including granular excrescences, subchorionic fibrin or subamniotic hemorrhage
  • Look at the integrity and extent of the vasculature, including any thrombosis and traumatic damage
Gross pathology of placental disorders.[1]
  • Examine the maternal surface (basal plate) for completeness, adherent blood clots, depressions, calcifications and fibrin
  • Take a membrane roll and cord sections, before sectioning the placenta
  • With the fetal surface down on the cutting board, cut the placenta at 1cm intervals so that it can be reconstructed.
Placental tissue after cutting, here showing severe intervillositis, with dark red and soggy tissue.
  • Palpate the parencyhmal sections for areas of induration.
  • Note the color of the parenchyma and describe any pale areas, cysts, infarcts (estimate total amount of infarcted tissue), thrombi, increased fibrin and calcifications

Tissue selection

  • Distal (toward fetus) membrane roll and cross section of distal cord. It should include the area of rupture.
  • Proximal (toward placenta) membrane roll and cross section of proximal cord ( 2-3 cm from insertion). They should include membranes up to the chorionic plate.

A membrane roll is created by cutting a strip, about 3 cm wide, of membrane, from the rupture site to the placental insertion. Hold the edge with forceps and roll it around the forceps, and then cut a transverse section of the roll.
Cord sections should be no thicker than 4mm.

  • Placental section including fetal surface ( full thickness if possible)
  • Placental section including maternal surface (full thickness if possible)
  • Any lesions or abnormalities

Avoid taking placental sections near the margin

Gross report

Placenta weight by gestational age.

Example in a normal case:

(A. Labeled with patient's name and medical record number. The specimen is received fresh and consists of a) placenta with attached membranes and umbilical cord. The membranes are tan-red( with a marginal insertion. The site of rupture is __ cm from the nearest placental margin. There is no accessory lobe.) The trimmed placental weight is __ gramsTemplate:Comprehensive-begin-Corresponding to the __th percentile for the gestational age)). The placental disc measures __ cm and varies in thickness from __ to __ cm. The umbilical cord is tan-pink and eccentrically inserted(, __ cm from the nearest placental margin, and measures __ cm in length, __ cm in proximal diameter and __ cm in distal diameter.) Cut sections of the cord reveal three blood vessels. The fetal surface is blue-pink, smooth with normal vasculature and << minimal / moderate / major>> subchorionic fibrin deposition. The maternal surface is complete with <<minimal / moderate / major>> physiologic calcifications. Sectioning reveals a red, spongy, homogenous parenchyma without gross lesions. (Representative sections are submitted for microscopic examination in 4 cassettes.)

KEY OF SECTIONS (example):

  • 1- distal membranes and umbilical cord
  • 2- proximal membranes and umbilical cord
  • 3- placental section including fetal surface
  • 4- placental section including maternal surface

Microscopy report

A small amount of intervillous neutrophils by the fetal surface like this is insignificant.
  • Look for inflammation, especially by the fetal surface in the intervillous spaces and around the fetal blood vessels.[notes 3]
  • At least if there is a suspicion of meconium in the amniotic fluid (from clinical history and/or the gross exam), look for the following histopathologic signs of it:[2]

Other relatively common findings

Microscopy report

Example of normal report:

((Placenta, <<vaginal/Caesarean>> delivery:))
Third trimester placenta with term villous histology. Placental weight (__ gm), at __th percentile for gestational age. Membranes without significant histopathologic changes((, negative for chorioamnionitis)). Trivascular umbilical cord, with no significant histopathologic changes((, negative for funisitis)).

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
  2. In contrast, in embryology and fetal medicine, the proximal umbilical cord refers to the segment closest to the fetus:
    - Wyburn GM (1939). "The formation of the umbilical cord and the umbilical region of the anterior abdominal wall. ". J Anat 73 (Pt 2): 289-310.9. PMID 17104757. PMC: 1252509. Archived from the original. . 
    Harvey J. Kliman, M.D., Ph.D. (2006-10-29). The Umbilical Cord (from The Encyclopedia of Reproduction). Yale School of Medicine.
  3. Minor inflammation in the decidua can be ignored as it doesn't have a clinical significance for the fetus.

Main page

References

  1. Chen, Yukun; Zhang, Zhuomin; Wu, Chenyan; Davaasuren, Dolzodmaa; Goldstein, Jeffery A.; Gernand, Alison D.; Wang, James Z. (2020). "AI-PLAX: AI-based placental assessment and examination using photos ". Computerized Medical Imaging and Graphics 84: 101744. doi:10.1016/j.compmedimag.2020.101744. ISSN 08956111. 
    - Fig 5- available via license: Creative Commons Attribution 4.0 International.
  2. Mandolin S. Ziadie. Placenta - Nonneoplastic placental conditions and abnormalities - Noninfectious - Meconium staining. Pathology Outlines. Topic Completed: 1 October 2011. Minor changes: 27 August 2020