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Second trimester hemorrhage: Placeta previa
Bleeding during pregnancy is extremely dangerous, its presence can pose an imminent risk to the fetus and the mother.
Thus, it has been possible to group the different causes of hemorrhage by trimester, the most frequent second trimester hemorrhages being placenta previa and premature detachment of the placenta.
What is the normal placenta like?
The feto-placental unit is an organ, since it is the intestine, lungs and kidneys of the fetus.
Thanks to the placenta, the fetus receives the nutrients and oxygen it needs for its development. In this sense, the characteristics of a normal placenta are.
Weight: 470 grams approximately
Circle shape
Diameter: 22 cm
Composed of: a placental disc, extraplacentral membranes and an umbilical cord that has three blood vessels.
Likewise, in the placenta two surfaces can be described, a maternal face, which is the face attached to the uterus, and a fetal surface.
Now, the really important thing is where the placenta is inserted. Normally, it must be inserted deep into the uterus.
What is Placenta Previa?
Placenta previa or low insertion of the placenta occurs when the placenta is located in the lowest part of the uterus, near the internal cervical os.
In addition, this happens from the 20th week of pregnancy, specifically, between the 26th and 28th week of gestation.
It is very common for it to happen to women who have already had children, with a probability of 5%, while nulliparous women only have an approximate 0.2% risk.
Why is it dangerous for the placenta to insert into the cervix?
The reason is that the cervix is made of a type of tissue that is not strong enough to support the placenta.
At the same time, it is a very thin and fragile area. Besides, it has an abundant blood supply.
Causes of placenta previa
More than causes, this second trimester bleeding is related to risk factors, which are.
Advanced maternal age
Multiparity, this is because inside the uterus are scars from previous implantations
Twin gestation
Caesarean section
Uterine tumor
Endometritis
Smoking
How does low insertion of the placenta occur?
There are several theories that try to explain the reason for this pathology. The first theory is dysfunction of the normally inserted placenta.
What happens is that in the first place is that the ovum implants where it belongs, but as the placenta develops, it is inserted in the lower part of the uterus.
Subsequently, it may happen that the endometrium is inadequate, so the placenta must be inserted in healthy areas of the uterine wall and, one of those areas is the lower part of the uterus.
Classification of placenta previa
It is classified according to the location of the placental disc in relation to the internal cervical os.
Occlusive center: it is when the placenta covered the entire internal cervical os.
Partially occlusive: occurs when the placenta covers a part of the hole.
Marginal: it is the placenta that is located 5 or 10 mm from the internal cervical os.
Low or lateral insertion: it is the placenta that is more than 3 cm, but less than 10 cm from the internal cervical os.
Fortunately, the most frequent abnormal implantation is low insertion, with a percentage between 37% and 54%. Also, bleeding may appear after week 36.
What are the symptoms of placenta previa?
The sign that alarms the woman is bleeding through the external genitalia. This bleeding is usually bright red and little to moderate amount.
Added to this, the bleeding is clot-free and painless. Also, it can appear while the woman is sleeping or resting.
However, blood loss is abundant when the patient has hypotension, tachycardia, paleness, and dizziness.
In addition to this, the presence of laboratory parameters that report a decrease in hemoglobin.
It should be mentioned that gynecological examination with vaginal examination is contraindicated in the placenta previa, especially the occlusive center and the partially occlusive one.
From the above it is clear that if they perform a touch they could generate severe bleeding and compromise the life of the woman.
How is the diagnosis of placenta previa made?
It is the sum of the risk factors, plus the symptoms that the patient and the ultrasound have presented.
Likewise, it is necessary to place a speculum to be able to visualize the walls of the vagina and confirm the exit of blood through the external cervical os.
For its part, with ultrasound what the obstetrician seeks is to identify the position of the placenta and, how it relates to the internal cervical os.
Also, a placental Doppler ultrasound is required to rule out other pathologies associated with the placenta such as placental accreta, which is when the placenta invades different thicknesses of the muscular wall of the uterus.
What is the treatment of placenta previa?
If the diagnosis of placenta previa is made and the patient is bleeding, she should be admitted to a hospital, in order to monitor fetal vitality.
What's more, the hospital will carry out the relevant tests. Additionally, the woman must have absolute rest, both physical and sexual.
On the other hand, the criteria for hospitalization should be considered, such as, for example, premature fetus.
Similarly, they administer lung maturation inducers such as dexamethasone or betamethasone, although after this practice there is some controversy with its long-term effect.
How is the follow-up of a patient with placenta previa?
After diagnosis, the controls are more rigorous, since it is a high-risk obstetric pregnancy.
Usually it should be done once a week. Monitoring should include an ultrasound scan to determine fetal vitality, whether there is fetal growth restriction or placental accreta.
