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What is Placenta Previa?

What is Placenta Previa?

Pregnancy
Apr 14, 2017

So you went to your prenatal anatomy ultrasound around your 20th week of pregnancy, and your health care provider now has told that you have a low-lying placenta. What is this called and what does it mean?

Typically, the placenta develops near the fundus, or top, of the uterus. In women with placenta previa, the placenta grows either right next to, partially covering, or completely blocking the cervix. This type of placental placement can cause a risk of excessive bleeding during labour and delivery, which can threaten the health and safety of both mother and baby. In most cases; however, the placenta moves up as it shifts with the growing uterus during the final weeks of pregnancy. Diagnosis of Placenta Previa happens in less than 10 percent of women with a low-lying placenta, and there are three types of classifications.


Marginal Previa

The edge of the placenta is too close to the opening of the cervix. The placenta may move upward as pregnancy progress, or it may partially block the birth canal. Your doctor or midwife will order another ultrasound to check on the location as you get further into your third trimester. Marginal Previa presents a risk of hemorrhage during labour and delivery if the placenta doesn’t move out of the way. While a vaginal delivery is possible in most circumstances, your physician may prefer to book a cesarean, if the placenta is still too close.


Partial Previa

In this instance, the placenta partly covers the cervical opening. Your physician will continue to monitor the location of the placenta by ultrasound throughout the rest of your pregnancy in hopes that the placenta moves far enough out of the way, but with this presentation that occurrence is unlikely. Due to damage to the placenta from the pressure of baby's descent during delivery, a vaginal birth would likely result in excessive bleeding. The obstetrician will usually schedule a cesarean birth a few weeks before natural delivery would occur, if the placenta continues to partially cover the cervix.


Total Previa

When the placenta completely blocks the cervix, it is rare that it will move completely out of the way before delivery. Issues with bleeding are likely to occur during pregnancy, and that can be quite alarming for you. Even if you don’t have an episode of breakthrough bleeding, your obstetrician will continue to monitor you and allow your baby to mature to where a cesarean birth will be necessary. You will be told to go to the hospital if any bleeding occurs. Additionally, you will be instructed to avoid stimulating the cervix, abstain from sex, vaginal manipulation, and douching. However, if you are having episodes of bleeding, the obstetrician will try to assess the maturity of the baby and the degree of blood loss. You may be treated with intravenous fluids to maintain fluid volume, and given blood or plasma transfusions to replace the blood loss. Fetal monitoring will be used to gauge the baby’s well-being. If the hemorrhage is severe, the baby will be delivered immediately by cesarean, even if the lungs are immature. The placenta in this condition cannot nourish the baby, and the severe blood loss places the mother at risk.


Experiencing a low-lying placenta in any form can be stressful and scary for you. Just remember it usually is detected early and managed by your health care team. Are you waiting to see if your placenta will move out of the way, or have you ever experienced complications from this previously?

Medicine Hat Doula

We encourage you to learn more about our "What in the World" series. Please see our A to Z index for a whole host of pregnancy, postpartum, and parenting information and terminology.


Loree Siermachesky works as a multi-certified labour and postpartum doula, certified Lamaze childbirth educator, certified breastfeeding counselor, certified placenta encapsulation specialist and a certified car seat technician in Medicine Hat and Lethbridge. She has had the honour of attending over 1400 births in the last 20 years. She is well-known and greatly respected by the medical providers in Medicine Hat, Lethbridge, Brooks, Taber, and Calgary. She cares deeply for this profession and even more for her clientele, honoring them in whatever method of birth they choose, or helping them transition to new parenthood as they wish.