Taking Charge of Your Health

Placenta previa means “placenta first,”
because the placenta is the first thing within the uterine cavity. In this condition, the placenta implants in
the lower uterus, close to or even covering the uterine opening, called the internal cervical
os, and it can therefore easily bleed, which usually happens after 20 weeks of gestation. Normally the placenta implants in the upper
uterus, and it’s unclear why it implants in the lower uterus. One hypothesis is that the placenta implants
lower down when the endometrium in the upper uterus is not well vascularized. In fact, endometrial damage from things like
a previous cesarean section, an abortion (which could be induced or spontaneous), uterine
surgery, and multiparity or multiple pregnancies can decrease vascularization and increase
the risk of placenta previa. In other cases, risk factors for placenta
previa include having multiple placentas or a placenta with a larger than normal surface
area, which can both happen with twins or triplets, as well as maternal age of 35 years
or more, intrauterine fibroids, and maternal smoking. Placenta previa is classified by how close
the placenta is to the cervical os, it can be complete where the placenta completely
covers the cervical os; partial where the placenta partially covers the cervical os;
or marginal where the edge of the placenta extends to within 2 cm of the cervical os. As the pregnancy progresses, the lower uterine
segment grows, and if the placenta’s in the lower uterus, this growth disrupts the
placental blood vessels, which can cause bleeding. This usually a sudden onset of painless bright
red bleeding that typically happens after 20 weeks gestation. The amount of bleeding can vary, and it can
be intermittent or continuous, sometimes increasing during labor because of uterine contractions
and cervical dilation. Complications on the maternal end are related
to the amount of blood loss, and fetal complications can include hypoxia and preterm delivery. Placenta previa is also associated with placenta
accreta, which is where the placenta invades the myometrium and becomes inseparable from
the uterine wall. Placenta previa is often diagnosed during
prenatal ultrasounds, but occasionally it’s not recognized until cervical changes during
labor cause bleeding to happen. For treatment or management, the main goal
is to plan for and prevent preterm birth, and to manage maternal bleeding. Corticosteroids can be sometimes given to
help enhance fetal lung maturity. For minor maternal bleeding, bed rest is usually
sufficient, but for major bleeding, blood products and intravenous fluids might be used
to support hemodynamic stability. In some severe cases, where the maternal hemodynamics
are worrisome and the fetal heart rate tracing shows signs of fetal hypoxia, an immediate
cesarean section can be performed. Alright, as a quick recap, placenta previa
describes a placenta that’s in the lower uterus instead of the upper uterus. The internal cervical os might be covered
completely, partially, or marginally, and this can bleeding that’s painless and bright
red, and can increase the likelihood of a preterm delivery and fetal hypoxia. Thanks for watching, you can help support
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