La previous placenta (or low placenta) is a condition in which the placenta adheres to the wall of the uterus in the lower part, therefore in an abnormal way.
At the beginning of pregnancy, the placenta is previa in 5% of cases and it is not a condition that should worry because it will most likely settle during the pregnancy as the uterus becomes enlarged and pushes the placenta upwards. But if the placenta subsides towards the end of the pregnancy it can be a problem.
If placenta previa is diagnosed around the 35-36th week, a cesarean delivery may often be required, especially if placenta previa is centrally located and therefore obstructs the cervix and would prevent the baby from channeling into the birth canal.
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Normally the placenta it should settle in the upper part of the uterine cavity and remain fixed in that position, guaranteeing all its important functions, first of all that of guaranteeing the metabolic and gaseous exchange between the blood of the fetus and that of the mother.
But in some cases the placenta can move to the lowest part of the uterine cavity.
It is not a diversi modi per to classify placenta previa, based on the distance between the edge of the placenta and the orifice of the cervical canal:
- marginal placenta previa: the distance does not exceed 3 centimeters
- lateral placenta previa: the distance is more than 3 cm from the orifice
- central placenta previa: the placenta covers the orifice completely
What happens in the case of placenta previa
The tissue that makes up the placenta is not extensible, so as the uterus grows, if the placenta is in the lower part, it will hardly be able to adapt to the dilation of theuterus.
Symptoms of placenta previa are essentially related to abnormal bleeding: the blood is bright red and there is no pain. A'echography will determine if it is placenta previa and the doctor will decide how to proceed: generally the progress of the situation is followed, keeping the placenta under close control and a caesarean section will be planned.
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What are the risks in case of placenta previa?
The risks for the child are mainly related to the possibility of a premature birth, to a reduced oxygenation caused by the detachment of the placenta in some points, to the blood loss caused by the lacerations of the placenta that also affect the blood vessels of the fetus.
For the mother, the risks are mainly related to hemorrhages, which can cause anemia, and obviously the mandatory use of a caesarean section.