If you’ve been diagnosed with a condition called placenta previa, you might be wondering what’s next for you in your pregnancy, and how you can plan for your upcoming birth.
Knowing what the condition is and the risks involved will make it easier to plan your care or future pregnancies with your health care provider.
Here’s everything you need to know about placenta previa.
What does the placenta do?
The placenta is a vital organ in pregnancy. It acts as the lifeline for babies until they’re born.
The baby receives blood, oxygen, and nutrients from the mother’s blood stream; these pass through the placenta and umbilical cord to the baby.
Learn more about this fascinating organ by reading our article What Is A Placenta? 13 Amazing Placenta Facts.
What is placenta previa?
Placenta previa (also spelt placenta praevia) is a placental abnormality that can cause possible complications in your pregnancy and birth.
Ordinarily, in early pregnancy, the placenta attaches wherever the fertilized egg has implanted in the uterine wall. This is usually in the upper to mid part of the uterus.
Placenta previa occurs when the placenta lies low in the uterus and fully or partially covers the cervix.
Placenta previa is classed as a high-risk pregnancy condition due to an increased risk of severe bleeding during pregnancy and birth.
If you’ve been diagnosed with placenta previa you will require careful follow-up care with your health care provider.
Placenta previa types
There are 3 types of placenta previa, classified according to how much of the cervix or cervical opening the placenta covers:
- Partial placenta previa; where the placenta partially covers the cervix
- Complete placenta previa; where the placenta completely covers the cervix
- Marginal placenta previa; where the placenta is lying close to the cervix, but does not cover it. This is also known as a Low Lying Placenta.
What causes placenta previa?
Placenta previa occurs in about 1 in every 200 pregnancies.
No one knows exactly what causes placenta previa, but there are certain risk factors a pregnant person might have, which would increase the risk of it occurring.
The risk factors are:
- Past pregnancy. The greater the number of pregnancies (over 20 weeks), the greater the chance of placenta previa.
- Previous placenta previa. Placenta previa in a previous pregnancy increases the chance of it occurring again
- Previous cesarean delivery. Uterine scarring can affect the development of the placenta
- Previous uterine surgeries (including uterine fibroid removal). Any surgery will cause scarring.
- Uterine fibroids. Fibroids take up space in the uterus, affecting the space available for the placenta to develop
- Multiple pregnancy. Being pregnant with twins or triplets can increase the risk.
What are the symptoms of placenta previa?
The most common symptom of placenta previa is painless vaginal bleeding.
This painless bleeding will be sudden, fresh, and bright red. It’s likely to occur in the second or third trimester.
In some cases of placenta previa, women will not have any bleeding during pregnancy.
Sometimes, placenta previa isn’t diagnosed until the time of birth.
What triggers bleeding in placenta previa?
Towards the second half of pregnancy the cervix begins to thin out and soften in preparation for your baby’s arrival.
During labor, the cervix has to thin and dilate in order for your baby to pass through the birth canal and for you to have a vaginal birth.
The part of the placenta that covers the cervix will become disrupted and will tear as the cervix begins to make changes.
This can happen during pregnancy or in labor.
It can cause severe bleeding as the placenta pulls away from the cervix.
Sometimes the bleeding will resolve itself but, if not, an emergency c-section will be required.
Remember that any bleeding from the vagina in pregnancy requires further investigation to assess your health, and your baby’s health.
Speak to your doctor or go to the hospital straight away if you experience any bleeding, even if it’s stopped. Seek emergency medical care if you have heavier bleeding.
To learn more about possible symptoms, read our article Placenta Previa | Symptoms And Bleeding.
What is the concern with placenta previa?
Due to the position of the placenta in placenta previa, the main concern is the risk of possible hemorrhage, which requires immediate medical care. If uncontrolled, the bleeding can be life-threatening to both mother and baby.
It’s important to remember the blood loss is coming from the mother, not the baby; it can, however, be quite significant to both.
Serious bleeding might require a blood transfusion for the mother, to support her well being.
What are the other risks of placenta previa?
In addition to the risk of serious bleeding for the pregnant woman, there might be additional health risks for her and for her baby:
- Higher risk of cesarean section
- Lack of oxygen supply to baby, due to blood loss
- Premature Labour or preterm birth
- Associated health risks to baby, due to prematurity
- Possible risk of hysterectomy, if placenta cannot be removed safely
- Increased risk of a small for gestational age baby
- Impact on any future pregnancy.
How is placenta previa diagnosed?
The only definitive way to diagnose placenta previa is with a scan; either an abdominal or transvaginal ultrasound might be used.
If placenta previa is present, it’s usually diagnosed during a second trimester ultrasound.
At this scan the sonographer will check the health of the baby but will also look for other potential concerns.
The sonographer will find the placenta’s location, to see if it lies low in the uterus. If it does, it will be checked to see whether it covers the cervix, or how close it lies to the cervix.
Placenta previa might be suspected with any episode of vaginal bleeding.
If the placenta lies across the cervix, any disruption to it can cause heavy bleeding as the placenta separates from that part of the cervix.
Placenta previa can affect your baby’s ability to get into a head down position, if the placenta lies in the lower part of the uterus. If your baby is persistently lying across the uterus, or in a breech position, placenta previa could be the cause.
Related reading: 8 Signs Your Baby’s Position is Affecting Labour.
Is placenta previa always the cause of bleeding in pregnancy?
Vaginal bleeding can be a symptom of Placental Abruption, where the placenta begins to separate from the wall of the uterus before the birth of the baby. This results in heavy bleeding.
Placental abruption is classed as a medical emergency and requires immediate medical attention.
It’s important to speak to your health care provider straight if you experience any bleeding.
Treatment for placenta previa
People often ask: how is placenta previa treated? Unfortunately, it cannot be treated; it can only be managed appropriately.
The goal will be to get you safely through pregnancy and as close to your due date as possible.
The location of the placenta will not change. Sometimes, however, in the case of marginal placenta previa, the placenta might be pulled up out of the way of the cervix. This occurs as the lower segment of the uterus thins out and the uterus grows in the third trimester, in effect taking the placenta with it.
The earlier placenta previa is diagnosed the better, as careful prenatal planning regarding your care can then be arranged.
Can I have a vaginal delivery with placenta previa?
Unfortunately, women who have been diagnosed with placenta previa will not be able to have a vaginal delivery, due to the placement of the placenta.
The placenta will obstruct the baby’s exit, making vaginal birth impossible.
If this is the case, a planned cesarean section will be arranged 2-3 weeks before your due date. This might have to be brought forward if certain events trigger bleeding before that, or if you show signs of labor prior to your arranged cesarean.
You can be prepared by familiarizing yourself with the early Signs of Labour, so you will know what to look out for, and by educating yourself on cesarean birth.
Placenta previa do’s and don’ts
If you’ve been diagnosed with placenta previa, your health care provider might make certain recommendations based on your circumstances.
Common advice includes:
- Bed rest. Your doctor might advise restricted activities following an episode of heavy bleeding
- Abstain from sexual intercourse (pelvic rest), particularly after bleeding
- Avoid heavy lifting or strenuous exercise, which can trigger bleeding
- Avoid vaginal examinations. Remember to inform any health professional that you have placenta previa and that internal vaginal exams should be avoided. A gentle speculum exam might be performed instead, to try to assess the causes of the bleeding. If previa is suspected, but not confirmed, a ultrasound should be performed, to check the placement of the placenta.