In a normal pregnancy, the placenta attaches to the top or upper side of the mother’s uterus. Placenta previa describes a potentially dangerous condition when the placenta partially or completely covers the mother’s cervix. Painless vaginal bleeding in the third trimester is a standard sign of placenta previa, but many cases present without any bleeding. An ultrasound can confirm or rule out placenta previa.
The following have been identified as risk factors for placenta previa:
- Previous placenta previa or Caesarian delivery
- Previous D&C (dilation and curettage), which can cause scarring to the uterine wall
- Smoking or alcohol/illegal drug use during pregnancy
- Large number of closely spaced pregnancies
- Carrying twins or multiple births
Women younger than 20 or older than 35 are particularly at risk for placenta previa.
Failure to recognize the signs of placenta previa (such as vaginal bleeding) or failure to perform a necessary emergency C-section can lead to catastrophic injuries to both the mother and baby—and in some cases, it can lead to death. Other serious complications include birth hypoxia and hypoxic ischemic encephalopathy (HIE), which can cause irreversible fetal brain damage. Placenta previa is also associated with low birth weight and an increased risk of premature birth. One of the more dangerous complications occurs when the placenta attaches to the muscle layer of the uterus (placenta accretia), which can cause life-threatening maternal hemorrhaging and may require a hysterectomy at the time of birth.
Treatment and Prevention
Avoidance of smoking, alcohol, and drugs can reduce the risks of placenta previa. It is important to tell your doctor your complete medical history, including any of the previously mentioned risk factors, and about any vaginal bleeding you experience. It is also essential to have proper pre-natal care, which should include routine ultrasounds that will detect a placental abnormality.
Treatment of placenta previa can involve bed rest and limitation of activity. Tocolytic medications (which inhibit contractions), intravenous fluids, and blood transfusions may be required, depending on the condition’s severity. A Cesarean delivery is required when the placenta completely covers the cervix.
Failure to diagnose or perform a timely C-section can result in the death or disability of the mother and baby.
Williams Obstetrics, 23rd Ed.
New England Journal of Medicine
Obstetrics – Normal and Problem Pregnancies, 5th Ed.
T. Russell – J. Tolliver, M.D.