One of the most common unexpected events during pregnancy is placenta previa or a low-lying placenta. The placenta is the baby’s source of support throughout the entire pregnancy. Through the placenta, the baby receives all the necessary nutrients to grow strong and healthy1.
The blood flow provided by the placenta contains both nutrients and oxygen for the fetus and it starts to form at the very moment the fetus implants into the uterus. The blastocyst (developing baby) divides into two parts, one will become the placenta and the other the baby. The problem arises when the placenta settles and attaches itself in a problematic spot for pregnancy.
What is Placenta Previa?
Placenta previa is characterized by its lower location in the uterus2. The ideal spot for the placenta is at the top of the uterus, but in some cases it is located below, very close to or on top of the cervix, which would significantly hinder a normal delivery.
A low-lying placenta may initially be situated low, but as the pregnancy progresses and the uterus grows, it rises and moves into the proper position. If by the 20th week the placenta is still partially previa, there is still time for it to rise and move into the correct position.
Explanatory Video
Types of Placenta Previa
There are three types of low-lying or previa placenta, each with its own risks and characteristics at different stages. The types of placenta previa are:
- Marginal Placenta: A type of placenta previa where it is only close to the cervix without causing any barriers or major problems for the pregnant woman. This type of placenta previa does not prevent a normal delivery from happening.
- Partial Placenta: A type of placenta previa where it partially covers (a piece of) the cervix. This type of placenta can indeed prevent a normal delivery.
- Total Placenta: This is the type of placenta previa that causes the most concern for doctors regarding delivery and other issues a previa placenta may cause. In this case, the placenta completely covers the cervix and did not move upward as the uterus grew.
Causes of Placenta Previa
Low-lying / previa placenta occurs without any apparent cause, it simply develops in undesirable locations, but several factors contribute to its happening. Twin pregnancy, where there would be more than one placenta; multiple previous pregnancies, different shaped uterus (bicornuate or septate, for example), or poorly done curettage that could result in scars, or surgeries for endometriosis removal.
Famivita Explanatory Video
The main problem that placenta previa brings for the pregnant woman is really at the time of delivery; for example, if she wants a normal delivery and has a total low-lying placenta, she would not be able to give birth naturally. Another issue caused by placenta previa is bleeding3.
Bleeding can happen at any stage of pregnancy and a simple movement by the baby can cause placental bleeding. Some cases of placenta previa or low-lying placenta are more delicate than others and are recommended to have bed rest to help control the bleeding.
If even then, rest is not enough, the woman may be hospitalized for closer monitoring. Some women may have placenta previa in pregnancy and not even notice! In fact, most cases are only diagnosed during imaging exams (ultrasound).
Placenta previa or low-lying placenta does not pose major risks to the mother or the baby. If there is a lot of bleeding during pregnancy, the doctor must provide support to the pregnant woman. However, in most cases, placenta previa resolves itself by the 36th week of pregnancy without any intervention being necessary.
