The placenta is a temporary organ that develops during pregnancy, acting as the life-support system for the developing fetus. It facilitates the exchange of gases, nutrients, and waste products between the maternal and fetal blood supplies. This organ sustains the growth and health of the fetus throughout gestation, and its appearance after birth offers important clues about the conditions of the intrauterine environment. A healthy, fully developed placenta reflects its successful performance in supporting the pregnancy.
Physical Characteristics of a Normal Placenta
A healthy, full-term placenta typically presents as a thick, disc-shaped organ, often described as resembling a pancake. Its average weight ranges between 500 and 680 grams, maintaining a consistent ratio of about 1:6 to the newborn’s weight. The size and thickness are proportional to the baby’s birth weight, indicating an appropriate surface area for exchange functions.
The organ has two distinct sides: the maternal surface (basal plate) and the fetal surface. The maternal side was attached to the uterine wall and has a rough, meaty texture. After separation, this surface should appear dark red or maroon and is visibly divided into 15 to 20 rounded lobes called cotyledons. These divisions are separated by indentations where maternal blood pools for nutrient transfer.
The fetal surface, known as the chorionic plate, is smooth, shiny, and covered by the translucent, grayish-blue amnion membrane. Large, branching blood vessels radiate outward from the center, where the umbilical cord attaches. These vessels spread across the surface to distribute blood to the chorionic villi. The uniform and clear appearance of this side confirms the integrity of the protective membranes.
Structural Components and Attachment
The architecture of a normal placenta includes the umbilical cord and the surrounding membranes. The umbilical cord typically contains three blood vessels: two umbilical arteries and one umbilical vein. These vessels are cushioned and protected by a gelatinous substance called Wharton’s jelly, and the cord usually measures between 35 and 70 centimeters in length.
The most common point of attachment for the umbilical cord is centrally located on the fetal surface. This central insertion allows for an even distribution of blood flow and nutrients across the organ surface. Variations, such as marginal or velamentous insertion, are noted because they can alter the efficiency of blood flow and place the vessels at risk.
The membranes surrounding the fetus are the amnion and the chorion, which fuse together during pregnancy. The inner amnion is tough and lines the entire amniotic cavity, extending over the fetal side of the placenta and the umbilical cord. These membranes attach firmly to the edges of the placental disc. Their completeness after delivery is important for ensuring no fragments remain inside the mother’s uterus.
Visual Indicators of Placental Health Issues
Calcification appears as hard, pale, or white areas on the placental tissue. While some degree of calcification is normal as the placenta ages near term, extensive or early deposition of these minerals can suggest impaired function or chronic stress, such as fetal hypoxia.
Pale, firm, or white areas on the maternal surface are often placental infarcts, regions of tissue death caused by blocked blood flow. Large or numerous infarcts reduce the functional surface area for exchange, potentially leading to restricted fetal growth. Conversely, large, dark clots on the maternal side are a visual sign of placental abruption, where the organ prematurely separates from the uterine wall.
Discoloration of the membranes and the placenta is a significant finding. Yellow or green staining indicates exposure to meconium, the baby’s first stool, passed while still in the uterus. Meconium staining is often associated with placental insufficiency and can be a marker for potential fetal distress.
Abnormalities in the organ’s shape, such as a bilobed or a succenturiate lobe, are also carefully inspected. A succenturiate lobe is an accessory lobe of placental tissue connected by blood vessels. These shape variations can complicate delivery and carry the risk that the accessory lobe or connecting vessels may be retained in the uterus after the main placenta is expelled.
Post-Delivery Examination and Significance
Following the birth of the baby, the expelled placenta is immediately examined by healthcare providers. This gross inspection is a standard part of the delivery process and offers an opportunity to assess the environment that sustained the pregnancy. The examination verifies the integrity and completeness of the entire organ, ensuring that no fragments remain in the uterus, which could cause postpartum hemorrhage or infection.
The provider checks the maternal surface to count the cotyledons and confirm no tissue is missing. The fetal side is inspected for the proper insertion of the umbilical cord and the number of vessels it contains. Noting any gross anomalies, such as discoloration, unusual texture, or focal lesions, provides diagnostic information that explains adverse outcomes like restricted growth or fetal distress.
The findings from this assessment are documented because they offer prognostic information for the newborn and the mother. Understanding the pathology of the placenta can inform future pregnancy management if structural or functional issues are identified. The appearance of this temporary organ serves as a detailed record of the entire gestational period.