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The placenta grows wherever the embryo implants itself in the uterus. In the majority of pregnancies, the placenta attaches at the top or side of the uterus.  In some cases, the embryo implants itself in the lower portion of the uterus.  Low-lying placenta is defined as a placenta ending within 2 cm of the internal cervical opening but not covering it.  If the placenta grows over the cervix, it is called placenta previa.  As the uterus expands it can pull the placenta higher, and away from the cervix, which resolves the situation.  The later in pregnancy that placenta previa exists, the more likely it will be present at the time of delivery.   This episode answers some questions about placenta previa resolving itself, and the risks involved with a low-lying placenta in the early and late stages of pregnancy.