Placental abruption – causes, symptoms, diagnosis, treatment, pathology

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. The maternal layer, the decidua basalis, is
literally a flattened out bag of blood with uterine arteries delivering blood in and uterine
veins pulling blood out. 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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