What is placenta previa? Causes of Placenta previa
Placenta previa is a pregnancy-related condition characterized by the abnormal positioning of the placenta, leading to potential complications for both the mother and the developing fetus.
Placenta Previa: Placenta previa is a condition where the placenta implants in the lower part of the uterus, either partially or completely covering the cervix. This abnormal positioning can lead to bleeding during pregnancy and delivery. There are different types of placenta previa, including total, partial, and marginal, depending on the extent of placental coverage.
Causes of Placenta Previa
Abnormal Placental Implantation:
One primary cause of placenta previa is abnormal placental implantation. Factors such as scarring from previous surgeries, uterine abnormalities, or a history of placenta previa in a previous pregnancy can contribute to the incorrect placement of the placenta within the uterus.
Maternal Age and Multiparity:
Advanced maternal age and multiparity (having multiple pregnancies) are associated with an increased risk of placenta previa. These factors may affect the structural integrity of the uterus and contribute to the displacement of the placenta.
Uterine Scarring and Cesarean Sections:
Previous uterine surgeries, particularly cesarean sections, can lead to uterine scarring. This scarring increases the likelihood of abnormal placental implantation and raises the risk of developing placenta previa in subsequent pregnancies.
How many types of placenta previa are there and what do they consist of?
Placenta previa is a condition in pregnancy in which the placenta is abnormally positioned, potentially leading to complications during childbirth.
Types of placenta previa
Placenta previa is divided into three main types based on the amount of placental coverage over the cervix. These types include total placenta previa, partial placenta previa, and marginal placenta previa.
Total Placenta Previa:
In total placenta previa, the entire cervix is covered by the placenta.
This type is associated with a higher risk of severe bleeding during labor and delivery as the cervix dilates, possibly necessitating a cesarean section.
Partial placenta previa:
Partial placenta previa involves partial coverage of the cervix by the placenta. This type allows for some degree of cervical opening during labor, but the risk of bleeding remains significant. Management may include close monitoring and, in some cases, cesarean section.
Marginal placenta previa:
Marginal placenta previa is characterized by the edge of the placenta reaching the edge of the cervical os without completely covering it. This type carries a lower risk of major bleeding than total or partial placenta previa, but still requires careful monitoring during pregnancy and delivery.
Why is it contraindicated to perform a Vaginal examination in cases of placenta previa?
Vaginal examination is contraindicated in cases of placenta previa due to the increased risk of severe bleeding and complications associated with this condition. Placenta previa occurs when the placenta partially or completely covers the cervix, creating a potential risk for blood vessel disruption and bleeding.
In cases of placenta previa, the placenta is in a position that obstructs or is very close to the birth canal. The placental blood vessels, which provide nutrients and oxygen to the fetus, are implanted in the uterine wall. If a vaginal exam is attempted, there is a high risk of disrupting these blood vessels and causing significant bleeding.
Bleeding: Disturbing the placental blood vessels during a vaginal exam can cause severe and life-threatening bleeding. The rich blood supply to the placenta makes it vulnerable to injury, and any disruption can cause rapid and significant blood loss.
Maternal and fetal complications: The bleeding associated with placenta previa can be harmful to both the mother and the baby. Maternal complications can include shock, infection, and the need for blood transfusions. For the baby, there is an increased risk of premature birth, low birth weight, and complications associated with prematurity.
Emergency situations: Uncontrolled bleeding from placenta previa can lead to emergency situations requiring rapid intervention, such as a cesarean section, to save the life of the mother and baby.
What is the type of placental abnormality. Why is it important to consider the patient’s gynecological history when she encounters a new pregnancy?
Placenta previa is a type of placental abnormality in which the placenta is located low in the uterus, either partially or completely covering the cervix. This condition poses a risk of hemorrhage during pregnancy and delivery.
A review of a patient’s gynecologic history is critical when considering a new pregnancy for several reasons:
Previous placental abnormalities: If a woman has a history of placental abnormalities, such as placenta previa in a previous pregnancy, there may be an increased risk of recurrence.
Previous cesarean section: Women who have had a previous cesarean section may have an increased risk of developing placenta previa in subsequent pregnancies. The scar tissue from a previous cesarean section may interfere with the implantation of the placenta, increasing the risk of placental abnormalities.
Uterine surgery or procedures: Any history of uterine surgery or procedures, such as dilation and curettage (D&C), may affect placental implantation. Scarring or changes in the lining of the uterus may affect placental attachment, potentially leading to complications such as placenta previa.
Reproductive health issues: The gynecological history can provide insight into a woman’s reproductive health, including any previous problems such as uterine fibroids, endometriosis, or structural abnormalities. These factors can affect the risk of placental abnormalities in subsequent pregnancies.
Previous pregnancy complications: Complications in previous pregnancies, such as preterm birth or miscarriage, may indicate underlying factors that could affect the current pregnancy. Addressing these factors early in prenatal care can help prevent or manage potential complications, including placental abnormalities.
Due to what situation has recurrent vaginal bleeding occurred in this patient?
This patient’s recurrent vaginal bleeding is due to placenta previa. Placenta previa occurs when the placenta covers the internal cervical os, causing bleeding during pregnancy. In this case, the patient presented with abundant transvaginal bleeding, bright red in color, with clots, for the past four months. The bleeding did not subside this time, indicating a persistent and worsening situation.
What is the reason why on the last occasion the bleeding did not stop, but instead increased?
The reason the bleeding did not stop and instead increased on the last occasion is likely due to the progression of placenta previa. Placenta previa can cause increased bleeding as the pregnancy progresses, especially as the uterus grows and the lower segment thins in preparation for labor. In this case, with the placenta completely covering the internal cervical os, the risk of hemorrhage increases, leading to the need for emergency cesarean section to address the life-threatening situation.
by Dr. Rezi
References:
1- Cunningham, F. G., Leveno, K. J., Bloom, S. L., Hauth, J. C., Rouse, D. J., & Spong, C. Y. (2018). Williams Obstetrics (25th ed.). McGraw-Hill Education.
2- Jauniaux, E., Alfirevic, Z., Bhide, A., Belfort, M., Burton, G., Collins, S., Dornan, S., Jurkovic, D., Kayem, G., Kingdom, J., Silver, R., & Sentilhes, L. (2018). Placenta Praevia and Placenta Accreta: Diagnosis and Management. BJOG: An International Journal of Obstetrics & Gynaecology, 126(1), e1–e48. https://doi.org/10.1111/1471-0528.15306
3- Jansen, C. H. J. R. (2020). Clinical challenges of a low-positioned placenta. [Thesis, fully internal, Universiteit van Amsterdam].