The placenta is an organ that forms shortly after conception for the purpose of providing necessary nutrients and oxygen to the growing fetus and removing waste products. This organ is very vascular, meaning that it has many blood vessels. Under normal conditions, the placenta positions itself on the upper wall of the mother’s uterus. A low lying placenta refers to a placenta that lies low in the uterus.
Placenta previa refers to a serious condition in which the entire opening of the cervix is blocked by the placenta. The danger of this condition is the risk of excessive bleeding that may occur during or prior to delivery. This condition is also associated with the risk of premature delivery. Placenta previa can be: total, in which the entire cervix is blocked; partial, in which only part of the cervix is covered; or marginal, in which the placenta is close to the cervix but is not actually blocking it. A low lying placenta is another name for marginal placenta previa.
Some women might experience cramping or spotting with a low lying placenta, although most women do not have any symptoms. The condition is first detected by ultrasound during the first 16-20 weeks of pregnancy. This condition occurs in about 5% of pregnancies, but the majority of these cases will resolve as the pregnancy progresses. This is due to the fact that as the baby gets bigger, the placenta often moves from the cervix.
In the cases of low lying placenta that do not resolve naturally, certain precautions will usually be taken as the pregnancy progresses. The mother will most likely be told to avoid most activities, and may even be ordered to bed rest for the remainder of the pregnancy. A cesarean section will almost always be performed. This procedure is necessary to prevent potentially heavy bleeding during delivery that would pose danger to the mother and the baby.
Although there is no single known cause of low lying placenta, several factors are associated with developing this condition. A previous cesarean section or other uterine surgeries, such as the removal of endometrial polyps via a dilation and curettage (D and C), appear to put women at a higher risk. Women who have had a low lying placenta in previous pregnancies are also at a higher risk. Other risk factors include having a larger placenta, such as in the case of being pregnant with twins or triplets, being over 35, being a smoker, or having an abnormally shaped uterus.