If a singleton placenta, weigh and measure in three dimensions (length, width, and depth). Measure the length and width of the attached umbilical cord. Note the site of insertion (central, eccentric, or velamentous-into the membranes). Make a fresh cut into the cord and note the number of vessels (normal is three). Note the presence of any true knots, false knots (convoluted fetal vessels), areas of hemorrhage, and/or rupture sites. Follow the fetal vessels along the placental surface (chorionic plate and confirm that they do no extend beyond the placental edge into the membranes. Examine the membranes for thickening, coloration (green pigment indicates meconium), opaqueness. Examine the maternal surface to determine the presence of all placental lobes (cotyledons). Look for areas of infarcts (yellow plaques) or calcification. Breadloaf the placenta substance and look for abnormal lesions. Submit one cross section of the umbilical cord, one section of the placental parenchyma with fetal surface (taken centrally) and a section of rolled fetal membranes. To roll the membranes, remove a strip of membranes with a portion of placental edge; roll the membranes towards the edge and pin the membranes to the edge. Trim the membranes and placenta to fit the cassette and either fix two or three hours in Bouin’s solution before placing into the cassette, or place the tissue and pin into the cassette for fixation in formalin (tell the technician).

 

Types of abnormal placentas:

 

               Battledore placenta-placenta with cord insertion at the placental edge.

 

               Extrachorial placenta: Origin of the fetal membranes inside the placental edge. Two types:

 

                         Circummarginate- membranes separate directly off the fetal surface.

                         Circumvallate- membranes overlap before separation, forming a thickened peripheral ring.

 

               Succenturiate lobe-accessory placenta within membranes connected to main lobe by bridging vessels. The presence of fetal vessels within the membranes extending to a rupture site implies a succenturiate lobe left inside the uterus.

 

               Placentas of multiple gestations are best described as a twin gestation with a fused single placenta. A placenta with single membranes and two attached placentas represents a monoamnionic monochorionic placenta (extremely rare), and can be processed as a singleton placenta with an extra cord. Twin placentas with a membranous septum represents a diamnionic gestation. To determine whether the chorion is either mono- or dichorionic, follow these principles

 

                 The septum in a dichorionic placenta is opaque and thick. The septum in a monochorionic placenta is almost transparent.

 

                 Separating the components of the dichorionic septum is difficult, and will demonstrate three layers. Separating the components of a monochorionic septum is very easy, and demonstrates two layers.

                  Fetal vessels are often seen crossing from one circulation to another in a monochorionic placenta. This can be best demonstrated by injecting colored dye or milk into arteries and veins from one cord, and determining whether the dye travels across the septum to the other fetal vessels. Note any vein-vein, artery-artery, or artery-vein anastomosis (arteries always run over veins).

 

               Each side of the placenta with an umbilical cord represents one gestation, and can be managed as a singleton placenta described above. Sections should consist of umbilical cord, membrane roll and placental section from each gestation, and a membrane roll from the septum, processed as described above.