During a labor contraction, the lower part of the uterus changes shape. The placenta is torn away from the uterine wall, causing bleeding.
Placenta previa is diagnosed in up to 5 percent of pregnancies at 4 months. However, by the time the baby is due, only 0.5 percent (1 in 200) women have a placenta previa.
Placenta previa is diagnosed by ultrasound. Because the cervix is very low in the body, a special ultrasound through the vagina (transvaginal ultrasound) may be needed.
Causes of placenta previa
- Prior cesarean section
- Prior uterine surgery
- Twins, triplets or more
Impact on pregnancy
You will probably not have any symptoms.
If the placenta is only slightly covering the cervix, or is just very close to the cervix, it will usually move away by your due date and you will probably not need to do anything different.
If the cervix is completely covered by the placenta and it stays that way until late in your pregnancy, you will need to have a cesarean birth as early as 5 weeks before your due date.
You may need an amniocentesis before the cesarean section to make sure the baby’s lungs are ready for birth.
You may be asked to decrease your activities, not have sex, or put anything in your vagina.
Some women need to go on bedrest, which often means no cooking, cleaning, laundry, or childcare responsibilities. Your provider will help you determine a safe level of activity.
- Bedrest does not mean isolation or not seeing friends and family.
- You can do special exercises while on bedrest to keep your muscles strong.
- If you have bleeding, you may need to be hospitalized for long periods.
Bleeding, with or without contractions, can be a complication of placenta previa.
- If bleeding is very heavy, you may need a blood transfusion or early delivery.
- Massive bleeding may threaten the life of the mother and the baby.
- If you have contractions during a bleeding episode, you may be given medication to stop the contractions.
- You may be given steroids to help the baby’s lungs develop faster. You would probably receive two injections, usually 24 hours apart. Sometimes the injections are repeated after one week. These steroids will not cause growth of facial hair or muscle development.
- Women with diabetes often have very high blood sugar after the shots. This is not a reason to avoid the shots. However, your blood sugar will need to be tested frequently, and you may need more insulin.
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