The placenta is an oval, flat group of cells attached to the uterus wall, formed during pregnancy. Its purpose is to transfer nourishment and oxygen to the fetus through the umbilical cord while eliminating waste products and carbon dioxide. In normal pregnancies, the placenta forms in the upper part of the uterus, allowing room for the fetus to grow. However, in some cases, the placenta will form very close to or even over the cervix (opening of the uterus), impairing normal delivery at birth. This is a condition known as placenta previa and there are various risk factors and symptoms associated with it. Placenta previa is also fairly simple to diagnose and manageable as far as treatment is concerned, especially with modern technology.
Placenta Previa and its Risk Factors
There are thre types of placenta previa:
- complete placenta previa – the internal cervical opening is completely covered by the placenta
- partial placenta previa – the internal cervical opening is partially covered by the placenta
- marginal placenta previa – the placenta is at the edge of the internal cervical opening
While most women will never experience the condition, there are certain risk factors associated with placenta previa:
- The fertilized egg is implanted very low in the uterus, causing the placenta to form close to or over the cervical opening.
- The placenta formed abnormally.
- The endometrium, or lining of the uterus, has fibroids, scarring or other abnormalities.
- multiple pregnancies (the risk doubles for these women)
- several previous pregnancies (odds go up to one in 20 with six or more)
Symptoms and Complications of Placenta Previa
There are several symptoms and potential complications that coincide with placenta previa. During the first and second trimesters, slight and occasional bleeding may occur. Sudden and excessive bleeding may happen in the third trimester. In fact, the main sign that a woman may be experiencing placenta previa is the discovery of bright red bleeding during the second half of pregnancy. The bleeding is not often accompanied by pain, but there may be some uterine cramping. Essentially, the bleeding occurs due to the placenta detaching as the pregnancy progresses. During the third trimester, uterine walls become thinner and spread to accommodate the growing fetus.
Placenta previa also carries with it possible complications. There may be insufficient blood supply to the baby, causing slow fetal growth. Additionally, fetal anemia may occur, there may be fetal distress due to low oxygen supply, shock or death of the mother from excessive bleeding, infection in the mother or formation of blood clots, or blood loss requiring a transfusion. For complete placenta previa, a C-section will be required.
Diagnosing and Treating Placenta Previa
Women may be diagnosed with placenta previa by an ultrasound showing the position of the placenta, but some women remain undiagnosed until delivery, especially those with marginal placenta previa. In many cases, if the diagnosis takes place before 20 weeks into the pregnancy, the condition may correct itself as the pregnancy progresses.
Other diagnostic signs of placenta previa include:
- a soft, relaxed uterus
- an abdominal ultrasound during the second trimester showing the low placement of the placenta
- a low-lying placenta shown by transvaginal or transperineal ultrasound
- the fetus is positioned horizontally in the uterus
Treating placenta previa is primarily aimed at minimizing any symptoms and making sure the pregnancy completes 36 weeks. The ultimate goal is safe delivery of the fetus by C-section as close to term as possible. Once placenta previa is diagnosed, further bleeding and complications may be avoided by making sure the mother has complete bed rest, sometimes in the hospital. Additionally, anything leading to the irritation of the cervix or uterine walls should be avoided, such as pelvic exams and sexual activity.
Placenta Previa and More Accurate Diagnosis
The largest danger of placenta previa is premature delivery because of heavy bleeding. However, with more and more accurate diagnosis of placenta previa due to better technology and greater knowledge of the condition, placenta previa is no longer a large threat to mother and baby as it once was.
Sources:
bodyandhealth.canada.com, "Placenta previa" (accessed May 22,2010)
mayoclinic.com, "Placenta previa" (accessed May 23,2010)
Mary Margaret Peralta - Mary Margaret is a mom to three children, with a passion for reading, writing and cooking.
Join the Conversation