Gross/Macroscopic Variations and Conditions

Variations in Size and Shape

Accessory lobe / bilobate placenta

Topic Completed: 1 September 2011

Minor changes: 23 February 2021

Copyright: 2002-2021,, Inc.

PubMed Search: Placenta accessory lobe OR succenturiate lobe

Mandolin S. Ziadie, M.D.
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Cite this page: Ziadie MS. Accessory lobe / bilobate placenta. website. Accessed November 29th, 2021.
Accessory lobe
  • One or multiple accessory lobes connected to the main disc by blood vessels that are at risk for hemorrhage and thromboemboli
  • Seen in 3% of placentas
  • Also called succenturiate lobe
  • Due to focal noninvolution of chorionic laevae
  • Gross description: main placental disc is attached to a smaller portion of placenta by fetal vessels and membranes
Bilobate placenta
  • Two lobes of equal size, separated by fetal membranes or connected by narrow isthmus of placental tissue
  • Umbilical cord inserts in the membranes between the two discs and is at risk for rupture
  • If incompletely removed, there is a risk of maternal postpartum hemorrhage
  • Gross description: two lobes of equal size separated by membranes
Gross images

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Accessory lobe

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