Pathological Disorders of the Placenta

Pathological Disorders of the Placenta

• The placenta is an organ connecting the fetus to the uterine wall, enabling nutrient intake, waste elimination, and gas exchange via the mother's blood supply.
• Pathology of the placenta encompasses disorders during pregnancy and the development of choriocarcinoma.

Placental Disorders During Pregnancy

• Placenta accreta: A rare condition where chorionic villi attach deeply to the myometrium, potentially penetrating it. Association with a deficient decidua makes placenta detachment challenging, increasing the risk of severe postpartum hemorrhage. Often linked to a previous operation. Three distinguishable forms exist, categorized by the depth of penetration.
  • Placenta accreta: Placenta grows into the uterine lining.
  • Placenta increta: Placenta grows into the uterine wall.
  • Placenta percreta: Placenta grows through the uterine wall, potentially reaching nearby organs like the bladder or colon.
• This disorder affects approximately 1 in 2,500 pregnancies.
• Placenta previa: In this obstetric disorder, the placenta abnormally attaches close to or covers the cervix, potentially causing antepartum hemorrhage. Hemorrhage can sometimes start in the later part of the first trimester but more frequently occurs in the second or third trimester.
  • Marginal previa: The placenta is next to the cervix but doesn't cover the opening.
  • Partial previa: The placenta covers part of the cervical opening.
  • Complete previa: The placenta completely covers the cervical opening.

Placental Abruption

• Placental abruption (Abruptio placentae): A serious pregnancy complication from placental separation from the uterine wall, causing late antepartum hemorrhage.
• It's a leading cause of late pregnancy bleeding and one of the major contributors to maternal mortality, affecting about 1% of pregnancies worldwide.
• Fetal mortality rates range from 20% to 40%, depending on the severity of separation.

Inflammation of the Placenta

• Inflammation is frequently linked to an infection, typically occurring via:
  • Ascending infection: Through the birth canal, leading to chorioamnionitis (inflammation of the chorion and amnion) and umbilical cord vasculitis.
  • Hematogenous infections: Deriving from maternal septicemia (blood poisoning), resulting in inflammation of the placental villi.
• Micro-organisms such as streptococci, toxoplasma, rubella, syphilis, cytomegalovirus, and herpes virus are potential causative agents. Fetal infection and abortion are notable complications. Septicemia of the mother, pelvic sepsis, and disseminated intravascular coagulation (DIC) are other potential complications.

Hydatidiform Complete Mole

• Hydatidiform complete mole: An abnormal pregnancy characterized by the absence of an embryo and enlarged, fluid-filled villi. Avascular villi are large due to fluid distension, often linked to chromosomal abnormalities invariably resulting in abortion.
• Villi are grape-like cystic structures, up to 1 cm (or more) in diameter, lacking an embryo, amniotic sac, or umbilical cord.
• The condition is more prevalent in women under 18 or over 40 years old, and the chromosomal makeup is typically 46xx, representing a paternal origin.
• The mole develops rapidly and often presents with an enlarged uterus or bleeding in early pregnancy. High levels of human chorionic gonadotropin (HCG) are a characteristic finding.
• A significant risk of choriocarcinoma (a malignant tumor) after hydatidiform mole is observed in about 2-3% of cases.
• Atypical villous hyperplasia is almost always present, and in approximately 10% of complete mole cases, an invasive extension of the hyperplastic villi can penetrate the uterine wall.

Partial Mole

• Partial mole: An abnormal placenta condition where only some villi are transformed into hydatidiform structures while fetal parts are grossly abnormal. Associated with triploidy due to fertilization by two sperm.
• Triploidy means the fetus has 69 chromosomes (instead of 46), largely consisting of one maternal set and two paternal sets of homologous chromosomes (69 xxy, or 69xxx or 69xyy).
• It isn't a true variant of hydatidiform mole. There is no consistent pattern relating degree of abnormality to risk of choriocarcinoma.

Choriocarcinoma

• Choriocarcinoma: A rare, highly malignant tumor of the placenta, arising from both cytotrophoblast and syncytiotrophoblast tissues. Typically associated with previous abortions, hydatidiform moles, or ectopic pregnancies.
• Etiology remains unknown.
• The tumor secretes human chorionic gonadotropin (hCG).
• Diagnosis often relies on serum and urine assays of hCG for monitoring and diagnosis.
• Microscopic examination reveals a soft, hemorrhagic mass within the uterus. Tumour cells are mononuclear trophoblast cells and multinucleated syncytiotrophoblast.
• Choriocarcinoma frequently spreads to other organs (lungs, liver, brain, vagina) early.
• Chemotherapy has a high response rate, and now, most patients can be cured.