GUIDE
Placenta previa occurs when the placenta partially or completely covers the opening of the cervix. It affects about 1 in 200 pregnancies at the time of delivery.
Many cases of placenta previa diagnosed on early ultrasounds resolve on their own as the uterus grows and the placenta moves away from the cervix. When it persists, careful management and delivery planning keep both mother and baby safe.
Be prepared from day one
The placenta normally implants in the upper portion of the uterus. In placenta previa, it implants low in the uterus and covers part or all of the cervix — the opening through which the baby would need to pass during vaginal delivery. This positioning makes vaginal delivery dangerous because the cervix cannot dilate without tearing the placenta, causing potentially life-threatening hemorrhage.
Placenta previa is usually diagnosed during the routine anatomy scan ultrasound around 18 to 20 weeks. Many early diagnoses resolve on their own as the uterus grows and the lower segment stretches, pulling the placenta upward and away from the cervix. Follow-up ultrasounds at 28 to 32 weeks confirm whether the previa has resolved or persists.
If you are in a high-risk pregnancy category due to placenta previa, your provider will work closely with you on a management plan tailored to the type and severity of your condition.
The terminology has evolved — some providers now use only 'placenta previa' (covering the cervix) and 'low-lying placenta' (within 2 cm but not covering it) rather than the older complete/partial/marginal classification.
The strongest risk factor is a prior cesarean delivery. The risk of placenta previa increases from about 0.5% after no prior C-sections to over 3% after three or more.
The hallmark symptom of placenta previa is painless, bright red vaginal bleeding in the second or third trimester. The bleeding occurs because as the lower uterus stretches and the cervix begins to change in preparation for labor, the placenta can tear slightly from the uterine wall.
The first bleeding episode (called a sentinel bleed) often occurs around 28 to 34 weeks. It is usually not heavy enough to be dangerous, but it serves as a warning. Not everyone with placenta previa bleeds — about one-third of cases are asymptomatic and found only on ultrasound.
Any bleeding in the second or third trimester should be reported to your provider immediately. Do not have a vaginal exam if you know you have placenta previa — digital cervical exams can trigger severe bleeding.
Even light bleeding with known placenta previa should be reported to your provider. Always use pads (never tampons) to monitor the amount.
If your provider has placed you on activity restrictions (pelvic rest, no heavy lifting, modified bed rest), follow them carefully. These restrictions exist to minimize the risk of bleeding. Pelvic rest means no vaginal intercourse, tampons, or vaginal exams. Ask your provider exactly what activities are and are not safe for your specific situation.
If you have a persistent placenta previa, pack your hospital bag by 28 to 30 weeks. Unplanned bleeding can happen suddenly, and having your bag ready reduces stress. Include important documents, phone chargers, comfortable clothes, and anything you would want if you need to be admitted quickly.
If you are Rh-negative, you will need a RhoGAM injection after any bleeding episode during pregnancy. Know your blood type and discuss with your provider. Your provider will also ensure that blood is available for transfusion if needed, especially as you approach delivery.
Complete placenta previa typically requires scheduled cesarean delivery around 36 to 37 weeks. If significant bleeding occurs before then, emergency delivery may be necessary at any gestational age. Discuss the plan for various scenarios with your provider so you feel prepared. A course of corticosteroids may be given between 24 and 34 weeks to accelerate fetal lung development in case of early delivery.
If placenta previa persists at the time of delivery, a scheduled cesarean is planned — typically between 36 and 37 weeks for uncomplicated complete previa, or at 37 to 38 weeks if the previa has not caused significant bleeding. Your provider may admit you to the hospital in the weeks before delivery if bleeding occurs, or if you live far from the hospital.
During the cesarean, the surgical team prepares for the possibility of heavier-than-normal blood loss. Having blood products available and an experienced surgical team are standard precautions. Most cesarean deliveries for placenta previa go smoothly.
If you also have signs of placenta accreta (placenta growing into the uterine wall), the delivery plan becomes more complex and may involve additional specialists.
Heavy bleeding from placenta previa can be life-threatening. Do not wait — go to the nearest emergency room immediately.
With proper monitoring and planning, the vast majority of pregnancies complicated by placenta previa result in healthy babies. Many placentas that appear low on early ultrasounds resolve on their own. For those that do not, a well-planned cesarean delivery at the right time keeps both mother and baby safe.
The key is regular monitoring, following your provider's activity restrictions, and knowing when to seek emergency care. For related information, see our guides on bleeding during pregnancy, placenta accreta, high-risk pregnancy, and subchorionic hematoma.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
