Placenta previa

[Tariq Zaki]

Placenta previa is attachment (implantation) of the placenta over the cervix, in the lower rather than the upper part of the uterus.

Women may have painless, sometimes profuse bleeding late in the pregnancy.
Ultrasonography can usually confirm the diagnosis.
Modified activity may be all that is needed, but if bleeding continues or if the fetus or woman develop problems, cesarean delivery is done.

Pregnancy complications, such as placenta previa, are problems that occur only during pregnancy. They may affect the woman, the fetus, or both and may occur at different times during the pregnancy. However, most pregnancy complications can be effectively treated.
Normally, the placenta is located in the upper part of the uterus. In placenta previa, the placenta is located in the lower part. It covers part or all of the opening of the cervix—the entrance to the birth canal. Sometimes the placenta is located near the opening of the cervix, not over it (called a low-lying placenta).
Placenta previa occurs in about 1 of 250 deliveries. During the 2nd trimester, as many as 2% of pregnant women have placenta previa. Placenta previa may be visible on ultrasonography. However, it resolves on its own in more than 90% of women before they deliver. If it does not resolve, the placenta may detach from the uterus, depriving the baby of its blood supply. Passage of the baby through the birth canal can also tear the placenta, causing severe bleeding.
Risk factors (conditions that increase the risk of a disorder) for placenta previa include the following:

Having had more than one pregnancy
Having had a cesarean delivery
Being pregnant with twins, triplets, or more babies (multiple births)
Having a structural abnormality of the uterus, such as fibroids
Having had a procedure that involves the uterus such as removal of fibroids from the uterus (myomectomy) or dilation and curettage (D and C) done several times
Smoking
Being older