Placenta previa

The  placenta  is that organ (normally) located near the fundus of the uterus , which supplies nutrients to the future baby through the umbilical cord. We speak of placenta previa when it is found at an unusually low level of the uterus, close to the cervix or when it even covers it.

If it’s diagnosed early in pregnancy, it’s usually not considered a problem. But if, in the later stages of pregnancy, she is still close to the cervix, this fact can cause bleeding which in turn can lead to other complications: even premature birth.

A woman with a patent placenta at the time of delivery of her baby will have to have a  caesarean section .

The position of the placenta is checked during the mid-pregnancy ultrasound  (usually between the  16th  and 20th week ), and also afterwards if necessary.

  • When it completely covers the cervix, it is called  occlusive placenta  (but also central placenta previa).
  • If, on the other hand, it rests on the edge of the cervix, it is called partial occlusive placenta  (or marginal placenta previa).
  • If its border is within two centimeters of the cervix but does not surround it, it is called a  low-insertion placenta .

What to do in these cases

What to do when diagnosed with placenta previa depends on how far along the pregnancy is. If your mid-pregnancy ultrasound shows placenta previa, don’t panic! In fact, as the pregnancy progresses, the placenta will probably “migrate” away from the cervix, and will therefore no longer be a problem.

  • Since it’s implanted in the uterus, the placenta obviously doesn’t move.
  • However, it can move away from the cervix thanks to the expansion of the uterus.
  • Also, as it grows, it will most likely direct its growth towards the rich blood resources located at the top of the uterus.

If placenta previa is identified on second trimester ultrasound , a follow-up ultrasound  in the beginning of the third trimester will be needed to verify its location. If in the meantime there is vaginal bleeding, an ultrasound will be done to find out what is happening .

Only a small part of women who – before twenty weeks – are diagnosed with an ultrasound scan with low or previa insertion placenta, will then present the same situation also at the time of delivery.

The placenta that completely covers the cervix – compared to the condition of a partial occlusive placenta, or that of a low insertion placenta – is more likely to remain in that position. However, placenta previa is present in only 1 in 200 deliveries.

When placenta previa persists

What can happen if placenta previa persists?

If the follow-up ultrasound finds that the placenta is still covering the cervix or if it is too close to it, the woman will be placed in a “pelvic rest” situation, which means not having intercourse or undergoing vaginal exams for the rest of your pregnancy. You will be advised to take it easy, to avoid activities that could cause vaginal bleeding such as strenuous exercise or strenuous activity.

However, when it is time to give birth, a  caesarean section will be necessary.

  • This is because – in the case of a total occlusive placenta – it blocks the baby’s way out.
  • But even if the placenta just surrounds the cervix, you will need to deliver via a C-section, as the placenta can bleed profusely as the cervix dilates.

There will probably be some painless vaginal bleeding during the third trimester.

In case of bleeding

If bleeding (or contractions) begins, hospitalization will be required.

Bleeding occurs when the  cervix  begins to thin or open (even just a little), which causes the blood vessels in that area to break.

What can then happen will depend, both on the stage of the pregnancy, and on how intense the bleeding is, and on how both the fetus and the woman are: in any case, if you accuse bleeding, and if you have a Rh negative blood group , you will need an injection of Rh immunoglobulin unless the father of the child is also Rh negative.

Nearing the end of the pregnancy, the baby will be delivered immediately via caesarean section. He will also be delivered immediately,

  • if he is still premature and if his conditions allow it,
  • or if you are bleeding heavily and continuously.

If not, you will be observed in hospital until the bleeding stops.

If you are less than  34 weeks pregnant,  you may be given  corticosteroids  to speed up the baby’s lung development and to prevent other complications should it be delivered prematurely.

You could be sent home,

  • if the bleeding stops and does not start again for at least a couple of days,
  • if, both you and the fetus are in good condition,
  • whether you can possibly access a hospital quickly in case the bleeding starts again.

However, sooner or later the bleeding will probably resume, and if this happens you will need to return to the hospital immediately.

If you and your unborn baby are still doing well and you don’t need to deliver immediately, a C-section will be scheduled at around  37 weeks , unless there’s a reason to do it sooner.

When deciding what to do, the doctors who follow you will evaluate the benefits of giving your child an extra period of time to mature, comparing these benefits to the risks of waiting longer, given that there is the possibility of having to face a new episode of heavy bleeding, and therefore having to perform an urgent caesarean.

The risks associated with placenta previa

Placenta previa makes you more likely to bleed heavily and need a blood transfusion. During and after childbirth. And here’s why.

After a baby is delivered via caesarean section, the midwife extracts the placenta, and Pitocin (a synthetic form of  oxytocin ) is often given to the mother along with other medications.

  • By helping to stop bleeding from the area where the placenta was implanted, Pitocin causes the uterus to contract.
  • But when you have placenta previa, it implants itself in the lower part of the uterus, which doesn’t contract as well as the upper part, and as a result, the contractions aren’t as effective at stopping bleeding.

Furthermore, probably women with placenta previa may have it implanted deeply and that it cannot be easily removed during childbirth. This condition is called placenta accreta.

to placenta accreta

Placenta  accreta  can cause heavy bleeding and may require multiple blood transfusions during delivery. This is a life-threatening condition that may require a hysterectomy to control bleeding.

The incidence of placenta accreta has risen in direct proportion to the increase in caesarean sections. This is because having previously had a cesarean section makes it more likely that a woman with placenta previa will also have placenta accreta. Indeed, as we have said, the risk increases dramatically with the increase in previous caesarean sections.

Finally, if there is a need to deliver before the deadline, the baby will be at risk of complications due to premature birth such as, for example, respiratory problems and low birth weight.

Possible risk factors

Most women with placenta previa have no apparent risk factors. However, if you have any of the following conditions you are more likely to have placenta previa:

  • you have already had placenta previa in a previous pregnancy,
  • you have had caesarean sections before,
  • you have had other surgery on the uterus,
  • you are pregnant with  twins or more,
  • you smoke cigarettes.

Other less important risk factors are represented by age, and by the number of births you have already had.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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