In placenta previa, the placenta (organ providing oxygen and nutrients from the mother to the baby) lies low in the uterus and covers (or partially covers) the cervix (narrow opening that connects the uterus and the vagina). It blocks the baby from coming out of the cervix. This is also called a low-lying placenta because the placenta is low and close to the cervix.
As pregnancy progresses and the uterus grows, mostly the placenta corrects itself and gets out of the baby’s way by itself. In a small number of cases, the placenta can get so low that it starts to touch the cervix, and there can be bleeding.
If managed well, mothers with placenta previa can give birth safely to healthy babies.
Research shows that placenta previa usually occurs in about 0.4% of pregnancies1.
Painless vaginal bleeding occurs during the second or third trimester. But in many cases, there are no symptoms.
If you are bleeding, and if placenta previa is suspected, it can be confirmed by doing an ultrasound scan.
If diagnosed before 20 weeks of pregnancy and the mother has no symptoms, the woman can lead a normal life.
But if diagnosed after 20 weeks of pregnancy and there is no bleeding, the mother is put on semi bed rest and monitored closely.
If diagnosed after 20 weeks and the woman starts to bleed, then the woman is asked to be on bed rest, refrain from sexual intercourse and is monitored closely. The goal is to keep the pregnancy going till the baby can be a term baby (36-37 weeks).
If the bleeding is heavy, the mother might need to be hospitalized until the mother and the baby have stabilized. Blood transfusions might be necessary if the bleeding is excessive. And iron and vitamin C supplements might need to be given.
If bleeding doesn’t stop and pre-term labour starts, the baby will need to be delivered by a c-section.
Effects on the baby
Placenta previa is a well understood condition and with proper management it can be handled smoothly. The risk occurs in the case of severe bleeding which may result in the baby having to be delivered prematurely.
What causes placenta previa?
The reasons are not known but it has been noticed that the following cases have high rate of placenta previa:
- Women who have had uterus surgery earlier. Especially if they have scars from the surgery.
- Women more than 35 years of age.
- Women carrying twins.
1. Faiz AS, Ananth CV.,"Etiology and risk factors for placenta previa: an overview and meta-analysis of observational studies", J Matern Fetal Neonatal Med 2003;13:175-90