Placental abruption
Definitions & Key takeaways
Placental abruption is a third-trimester obstetrical complication whereby the placenta prematurely detaches from the uterine wall leading to heavy bleeding and decreasing the amount of oxygen and nutrients that reach the fetus. Risk factors include cocaine abuse, trauma, smoking, hypertension, and preeclampsia.
Symptoms include vaginal bleeding, abdominal pain, and back pain, and if not treated promptly, it can lead to preterm labor, fetal distress, and even death. Management is with emergency cesarean delivery if there is fetal or maternal jeopardy. In-hospital observation may be opted for if the mother and fetus are stable and not term.
Placental abruption is the premature separation of all or even just a part of the placenta from the uterine wall, resulting in hemorrhage, or bleeding.
This usually happens after about 20 weeks of gestation, and affects about 1% of pregnancies worldwide. The placenta forms where the embryo attaches to the uterine wall and it’s a unique organ because it develops from both the mom and the fetus, and it’s job is to permit gas and nutrient exchange between them.
The word “placenta” literally means “flat cake.” So picture it as a cake with two layers, the maternal layer and a fetal layer.
But unlike other parts of the circulatory system where blood stays within narrow blood vessels, the decidua basalis is a huge pool of blood.
The fetal layer of the placenta on the other hand is called the chorion, which is a tissue that has fingerlike projections called chorionic villi which contain tiny fetal arterioles and venules.
These villi push into the decidua basilis, like tiny fingers reaching into a warm pool of oxygen-rich maternal blood. Gases and nutrients move back and forth between the decidua basalis and the fetal veins, by diffusing through the tissue layer of the thin chorionic villi.
Placental abruption happens when there is a separation of the uterine wall and decidua basalis. This separation is usually caused by degeneration of the uterine arteries that supply blood to the placenta typically from chronic problems like smoking or hypertension.
These diseased vessels rupture, causing hemorrhage and separation of the placenta. If the separation is near the margin of the placenta, it can cause vaginal bleeding, but if the separation is more central, there might be a pocket of blood that stays concealed between the decidua basalis and the uterine wall.
Placental abruption can be classified as partial or complete, depending on the degree of separation from the uterine wall.
As well as apparent or concealed, depending on whether vaginal bleeding is seen or not. Risk factors for placental abruption include acute events like blunt trauma from a car crash, fall, or domestic violence.
This can happen because the placenta is less elastic than the uterus, the strong forces from traumatic events like these can cause the placenta to sheer away from the uterine wall.
Also use of certain drugs are risk factors, like cocaine and methamphetamine b because these can cause significant vasoconstriction of the placental blood vessels and an abrupt increase in blood pressure, increasing the risk of an abruption.
Other risk factors include multiparity or multiple pregnancies and a maternal age over 35 years old. Interestingly, the strongest risk factor for placental abruption is having had a previous abruption.
Placental abruption is often accompanied by pain in the area of the abruption, and the uterus may tense up and become rigid as the strong muscular layer contracts to clamp down on the uterine vessels to reduce the bleeding Given that placental abruption leads to a serious blood loss from large vessels, it’s considered an emergency.
Maternal complications include hypovolemic shock, Sheehan syndrome which is a type of perinatal pituitary necrosis that results from hypovolemia, as well as renal failure.
Also, disseminated intravascular coagulation, or DIC, is also a possible complication, since the decidua basalis layer is also rich in thromboplastin, so an abruption causes the release of large quantities of thromboplastin which causes widespread clotting.
Fetal complications include intrauterine hypoxia and asphyxia because the fetus is no longer receiving adequate placental perfusion, and finally there’s an increased risk of premature birth.
Generally a diagnosis is made based on imaging, typically an ultrasound will show a retroplacental collection of blood, also blood or blood-stained amniotic fluid might come from the vagina.
Treatment depends heavily on the physiologic status of both the mother and the fetus, as well as the gestational age of the fetus.
The main approach is to use intravenous fluids and blood products to support the circulating volume and prevent a coagulation disorder from causing problems.
If the mother and fetus are stable, and the pregnancy is not far enough along, then it might be ideal to monitor the pregnancy closely while the fetus develops.
Alternatively, if the hemorrhage is severe or if there is evidence of fetal compromise, then an emergency cesarean section may be needed.
All right, as a quick recap, placental abruption is the premature separation of all or part of a normally implanted placenta from the uterine wall, which results in hemorrhage.
Complications depend on the degree of hemorrhage and how far along the pregnancy has advanced, and treatment focus on hemodynamic support until a safe delivery is possible.
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