Placenta Previa


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is placenta previa?

Placenta praevia is a complication of pregnancy in which the placenta the organ that connects the mother’s and baby’s blood supplies develops in the lower section of the uterus, thereby covering the cervix, through which a baby must pass during vaginal delivery. The placenta develops close to where the early embryo has implanted in the wall of the uterus, which normally happens in the upper region of the uterus, called the fundus. However, if the embryo implants lower down, generally the placenta will develop lower down as well. The reasons for this are not clear, but one possibility is that there is a reduction in the number of blood vessels in the fundus, making it a less valuable place for implantation. Some researchers have hypothesized that this can result from previous damage to the fundus, during a spontaneous abortion (miscarriage) or a cesarean section (C-section). Another reason for placenta previa is a multiple pregnancy. In most cases of twin and higher pregnancies, each developing baby has its own placenta and there simply is not enough room for all of them to implant in the fundus and for all placentas to attach at the fundus, and so one or more end up attached lower.

How common is placenta previa during pregnancy?

Placenta previa develops in about 5 per 1,000 pregnancies. However, several factors can increase the chances that you will have a placenta previa. One such risk factor is that you had a placenta previa in a previous pregnancy. Another risk factor is a multiple pregnancy; if you are carrying twins, triplets, or a higher number of babies, placenta previa is more likely than if you have a singleton pregnancy. Other risk factors are maternal age over 35 years, smoking and cocaine use, and especially history of surgery on the uterus. The latter includes a previous C-section and removal of uterine fibroids.

How is placenta previa diagnosed?

Your history and physical examination provide the doctor with the most important clues as to whether you may suffer from placenta previa. If you have suffered placenta previa in the past, this is a clue, as is a history of surgery on the uterus, including a C-section. Most important is what is happening to you at the current time. If you are experiencing heavy bleeding with little or no pain, this strongly suggests placenta previa. Some women with placenta previa also may experience premature contractions, but your obstetrician will use ultrasonography to confirm the diagnosis by actually visualizing the location of the placenta.

Does placenta previa cause problems during pregnancy?

Placenta previa can lead to severe hemorrhage (bleeding) and premature birth. Since the placenta blocks the cervix, vaginal delivery can cause a particularly severe hemorrhage which can threaten the life of the mother.

Does placenta previa during pregnancy cause problems for the baby?

Severe hemorrhage, due to rupture of the placenta during delivery, can lead to perinatal death (death of the baby just before or during delivery, or of the newborn just after birth. Even without placental rupture, placenta previa can cause premature labor and delivery, which increases the risk of medical issues for the newborn, including low birth weight and breathing problems.

What to consider about taking medications when you are pregnant or breastfeeding:

  • The risks to yourself and your baby if you do not treat the placenta previa
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat placenta previa during pregnancy?

Placenta previa is an anatomic problem, and thus cannot be corrected with medications. The placenta is simply located in a bad place. The principal management strategy is to deliver the baby through a C-section, which enables the baby to exit the mother without passing through the placenta that obstructs the cervix. In some cases, however, medications are needed for emergencies resulting from placenta previa. If the woman has a sudden onset of severe bleeding and labor contractions, for instance, medications are given to stop the labor (tocolytic drugs) and to constrict blood vessels of the uterus to slow bleeding. In the event that the woman has lost a large amount of blood leading to unstable blood pressure, medications will be needed that affect the blood vessels and heart action, while fluids will be given, along with any needed blood products, such as packed red blood cells. All of these types of drugs are given on a short-term basis to manage the emergency, so the risk from the drugs on the baby are minor compared with the potentially fatal consequences of not managing the emergency.

To prevent pain during the C-section the woman will be given epidural or spinal anesthesia, but this will be timed, and anesthetic drugs will be selected, so as to avoid risk to the baby. One other category of drugs given often in the setting of placenta previa is corticosteroids, particularly a steroid called betamethasone. This is given when the need to perform the C-section is urgent, but the pregnancy is not close enough to term for the baby’s lungs to be adequately developed. Generally, this means that the delivery is to occur prior to about 35 weeks gestation, but in some cases corticosteroids may be given to mothers who are to deliver any time up to 37 weeks, just to be safe. Whatever the case, corticosteroids are safe for the developing baby; in fact, the baby is the target of these medications.

Who should NOT stop taking medication for placenta previa during pregnancy?

Nobody who requires an emergency medication to stop labor, or to stabilize blood pressure can avoid the medication as she would be at risk of death. If you require corticosteroids to mature the baby’s lungs in order for the baby to be delivered early, it is not recommended to refuse this treatment, as avoidance would be putting the newborn at serious risk of breathing complications.

What should I know about choosing a medication for my placenta previa during pregnancy?

You may find Pregistrys expert reports about the individual medications used to treat this condition in here. Additional information can also be found in the sources listed at the bottom of this report.

What should I know about taking a medication for my placenta previa when I am breastfeeding?

By the time you are breastfeeding, you are past the time of emergency that involves bleeding late in pregnancy, or during delivery, and past the time of receiving corticosteroids to mature the babys lungs. Placenta previa is a good example of an obstetric emergency that is over when delivery is over, so long as your cardiovascular system has been stabilized.

What alternative therapies besides medications can I use to treat placenta previa?

As noted earlier, medications are given for support, and the main management strategy is delivery of the baby by way of C-section.

What can I do for myself and my baby when I have placenta previa during pregnancy?

Cooperate with your physicians. If severe bleeding begins, placenta previa becomes an emergency, and you need to assume the
patient role.

Resources for placenta previa in pregnancy:

For more information about placenta previa during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or check the following links:


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Last Updated: 09-03-2020
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.