Placenta previa will occur in approximately one out of every 200 pregnancies, according to the March of Dimes. This condition occurs when the placenta implants low in the uterus and covers the internal opening of the cervix. Pregnant women with placenta previa in the third trimester may require hospitalization and will need to deliver their babies by cesarean section to avoid risk to the mother and baby.
Types
Three types of placenta previa may occur during pregnancy. When the placenta is against the cervix but does not cover the opening, it is called marginal placenta previa. When the placenta only covers a portion of the cervical opening, it is called partial placenta previa, but when it covers the entire cervical opening, it is called complete placenta previa.
Risk Factors
Although there is no way to predict when placenta previa will occur, it is more common in some women than others. The March of Dimes states that women who smoke, use cocaine or are over the age of 35 may be at a higher risk of placenta previa. Those who have previously given birth through cesarean section, have had uterine surgery, have had twins or triplets and those with more than one child also experience placenta previa more commonly than women who do not, according to the American Pregnancy Association.
Causes
Several different factors may cause placenta previa. Abnormal formation of the placenta, an abnormal uterus, a large placenta and scarred endometrium tissue are all possible causes of placenta previa, according to the National Institutes of Health.
Symptoms
Painless, sudden bleeding from the vagina during the late second or early third trimester of pregnancy is the main symptom of placenta previa. This bleeding is usually bright red in color and can range in flow from light to very heavy. It may be sporadic, stopping on its own before starting up again. Cramping or uterine contractions may also occur with the bleeding.
Warning
Placenta previa can cause dangerous complications, according to the Mayo Clinic. If a woman goes into natural labor with placenta previa, there is a risk of bleeding or hemorrhaging so severe it may cause maternal shock or even death. Severe bleeding may also force an emergency C-section before the baby is full term and ready to be born. Finally, placenta previa can cause a rare condition called placenta accreta, which occurs when the placenta does not detach from the uterus after delivery like it's supposed to. Placenta accreta can require a hysterectomy, which is the surgical removal of the uterus. Because of these potential complications, a doctor should monitor all women with placenta previa very carefully throughout the pregnancy.
