What Are the Common Causes of Blood in Placenta?

Bleeding during pregnancy can occur for several reasons, but heavy vaginal bleeding might be cause for alarm, because it might be a sign of blood in the placenta. Bleeding during pregnancy is somewhat common, but when the source of this is blood in the placenta, the assistance of a doctor is almost always needed. To determine whether the placenta is bleeding or a more benign cause exists, a medical provider should be contacted at the first sign of blood. Oftentimes, the causes of blood in placenta are one of two problems: placenta previa or placental abruption. This is particularly important if the bleeding takes place during the third trimester, because this is when most problems involving the placenta tend to arise; bleeding during the first 12 weeks is usually caused by medical conditions unrelated to the placenta, however.

Placenta previa is the most common reason for blood in placenta. This medical condition occurs when the placenta is too low in the uterus during pregnancy, thereby partially or fully covering the cervix. In a healthy pregnancy, the placenta moves to the top of the uterus as the uterus grows, so that the cervix is open for the baby to pass through during birth.

By the second or third trimester, a placenta that is lying low will begin to painlessly bleed. It might hemorrhage or stop bleeding abruptly, only to start again several days later. Treating blood in placenta caused by previa usually requires plenty of rest and possible blood transfusions, depending on the amount of blood loss.

Placental abruption is another cause of blood in placenta. The human placenta usually is connected to the inner uterine wall during pregnancy. Placental abruption takes place in about 1 percent of pregnancies in the third trimester, and it occurs when the placenta partially or wholly becomes detached from the uterus, which can rupture blood vessels that normally connect the two structures.

This phenomenon can create problems for the baby, because it will not receive adequate nutrients or oxygen through the placenta, and the bleeding placenta can lead to dangerous blood loss for the mother. Bleeding is one potential symptom of abruption occurring, and it is often accompanied by intense stomach pain. If abruption is the cause of blood in the placenta, it requires a visit to the emergency room, because the life of the child and the health of the mother can be in jeopardy.