Placenta previa is a condition in which the placenta does not adhere to the bottom of the uterus, but part or all of the placenta adheres to the lower part of the uterus and cervix, causing uterine bleeding during pregnancy and obstructing the fetus's path when the mother goes into labor. There are 4 common types of placenta previa in pregnant women: central placenta previa, low-lying placenta previa, marginal placenta previa, and semi-central placenta previa.