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Placenta

Miscellaneous

Grossing placentas


Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 8 December 2011, last major update December 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Strategies and indications for placental examination
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● Institutions vary widely on the strategies they use to determine which placentas are examined
● Some of these include “embed and hold”, examination performed for specific indications, or examination of all placentas

Specific indications include:
● Clinician concern
● Maternal conditions (diabetes, hypertension, prematurity, postmaturity, history of reproductive failure, oligohydramnios, fever, infection, substance abuse, repetitive bleeding and retroplacental hematoma)
● Fetal conditions (stillbirth or perinatal death, multiple births, congenital abnormalities, growth retardation, prematurity, hydrops, thick meconium, admission to intensive care, APGAR score of 0-3 at 5 minutes, neurologic problems, fever and infection)
● Gross placental abnormalities

Membranes
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● Measure the point of membrane tear nearest to the disc, if identifiable
● Evaluate the color, odor and opacity of the membranes:
     ● Yellow-gray is suspicious for chorioamnionitis
     ● Green-brown is suspicious for meconium
     ● Describe the membranous insertion (normal / marginal, circummarginate or circumvallate)
     ● The membranes may double back on themselves to form a constricted, thick rim around the placental disk (circumvallate insertion) or wider, thin rim (circummarginate insertion)
     ● The percent of circumvallate insertion should be evaluated
     ● A sample of the circumvallate insertion site should be obtained and submitted as an additional disc section
● A strip of membrane, including the point of membrane tear, should be obtained
● Beginning with the point of tear, the strip is rolled around a long, thin probe with the amnion facing inward
● The roll is then fixed for a minute with an acidic fixative (e.g. acetic acid) and sectioned
● At least two spiral cross-sections should be submitted
● Trim the remaining membranes from the margin

Umbilical cord
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● Color
● Insertion (central, eccentric, marginal or velamentous)
● When the cord is inserted within the membranes (velamentous insertion), the intra-membranous vessels, unprotected by Wharton’s jelly, are at greater risk for compression and rupture
● Their presence and intactness within the membranes should be assessed
● The cord’s number of vessels should be assessed in the middle or fetal third of the cord to avoid miscounting caused by occasional vessel fusion near the placental surface
● Note the presence of any other abnormalities (hematomas, cord knots, strictures, thrombi or necrosis)
● Sample at least two representative sections of the cord (one from the fetal end and one from the placental end) at areas away from sites of trauma
● Any abnormalities should also be sampled

Disc
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● All measurements, including weight, should be obtained after removing the umbilical cord, fetal membranes and non-adherent blood clots
● Measure the disc in three dimensions (greatest major and minor horizontal lengths and thickness) and weigh it
● The placental weight should be compared to a table of standards based on estimated gestational age
● Describe the placenta’s shape and location
● Placentas may have one or more lobes that may or may not be connected
● Observe the fetal surface, which is usually shiny, red-grey and semi-translucent with vessels coursing over its surface
● It should be assessed for color, opacity, subchorionic fibrin (thick, pale deposits), subchorionic hematomas, squamous metaplasia, amnion nodosum or other lesions
● Flip the placenta and evaluate the maternal surface, which (in the term infant) is dark red and divided into lobules or cotyledons
● Extremely preterm placentas may be pink or tan
● The placental disc should be inspected for color, intactness, adherent clot or hemorrhage and any other lesions
● Missing cotyledons or extremely fragmented parenchyma, which may be indications of retained placenta, should be noted
● Serially section the disc at 1 to 2 cm intervals and examine each slice for intra-parenchymal lesions (e.g. masses, pale infarcts, lace-like bands, etc.)
● The size of all abnormal lesions should be estimated based on the percentage of the disc they occupy
● Obtain at least two full-thickness sections (including maternal and fetal surfaces) from separate, central areas of the disc
● Sections of any grossly identified abnormalities should be submitted in addition to these
● The sections of thick discs may need to be halved and placed into two cassettes in order to provide complete sections (including both maternal and fetal surfaces)

Special considerations for twin placentas
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● In addition to the standard features evaluated on gross examination of the placenta, there are special considerations when examining placentas from multiple gestations
● The most important key to examination is to ensure that descriptions and sections are clearly marked for each twin
● Include the number of discs (single or multiple), features of the dividing membranes (which may give a gross suggestion as to chorionicity: thin translucent membranes on a single disc are monochorionic, while thick, ridge-forming membranes on a single or dual disc are dichorionic), discordant size or appearance and presence of vascular anastamoses (which may indicate a twin-twin transfusion syndrome in monochorionic twins)
● In addition to the standard sections described above, representative sections of the dividing membranes and of any vascular anastamoses should be submitted

Artifacts
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● Caused by: freezing placenta (distorts villi, obscures meconium), Bouin’s fixative (obscures fusobacterium, hinders cytochemical staining), formalin fixation (distends fetal vessels, increases weight by 8%, Arch Pathol Lab Med 1991;115:726)

Gross dictation
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● Received in _____, labeled _______, is a discoid placenta that weights ____ g when trimmed of membranes and cord
● The membranes are tan-brown and translucent with minimal adherent blood clot
● The cord is inserted ___, has __ vessels, is __ cm long and __ cm in diameter
● The maternal surface is intact
● The fetal surface is unremarkable
● Cut surfaces show beefy red parenchyma, but no significant areas of infarct or hemorrhage or other gross abnormalities (or describe any gross abnormalities as appropriate)

Additional references
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Practice guidelines from CAP:
● Surgicals (Arch Pathol Lab Med 1997;121:449)
● Perinatal autopsies (Arch Pathol Lab Med 1997;121:368)

End of Placenta > Miscellaneous > Grossing placentas


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