Definition When the placenta implants over or near the inner opening of the cervix, the condition is called placenta praevia. The cervix is the opening of the uterus. As the cervix dilates during labour, the abnormal location of the placenta may cause heavy vaginal bleeding and keep the baby from travelling through the birth canal.
What is going on in the body? Placenta praevia occurs in 1 out of 200 births. In about 10% to 20% of these cases, the placenta covers the entire cervix. This is complete placenta praevia. Otherwise, only part of the cervix is covered. This is called partial placenta praevia.
Vaginal bleeding typically occurs:
as the lower part of the uterus starts to widen and thin out as the uterus grows in the later part of pregnancy
as the cervix opens during labour, which tears blood vessels in the placenta
with trauma to the placenta, as with the pressure of the penis during intercourse
The extent of the bleeding depends upon how much of the placenta covers the cervix and how many blood vessels are torn.
What are the signs and symptoms of the condition? Though symptoms differ, they may include:
sudden, painless, bright red vaginal bleeding, usually in the later half of pregnancy
painless vaginal bleeding after sexual intercourse
uterine cramping with the bleeding
bleeding during labour
What are the causes and risks of the condition? A woman is more likely to have this condition if:
she has had 6 or more births
she is carrying two or more foetuses
she previously had a caesarean section
she is older than 35 years
the placenta is large or abnormal
What can be done to prevent the condition? There is no known way to prevent this condition.
How is the condition diagnosed? Every woman with vaginal bleeding who might have this condition should be hospitalised and evaluated. The bleeding may become a haemorrhage without warning.
finding the foetus's position by feeling the mother's abdomen. In about one-third of the cases of placenta praevia, the baby is lying sideways or buttocks-first in the uterus.
full blood counts, or FBCs, to follow the mother's blood losses
In many cases, placenta praevia causes no symptoms and detected only by pregnancy ultrasound in the early second trimester. In these cases, no symptoms may ever occur and the placenta later may become normally situated.
What are the long-term effects of the condition? When a partial placenta praevia is found early in pregnancy, it may be managed or change so that a vaginal birth is possible. Complete placenta praevia usually calls for a caesarean section when the foetus is mature or if the mother starts to bleed heavily.
must have a hysterectomy if the placenta will not separate from the uterus
While the mother is usually fine, birth trauma or a haemorrhage may harm the baby. In 15% to 20% of cases, the baby dies. This may be due to not getting enough oxygen in the uterus, prematurity, or other causes of foetal distress.
What are the risks to others? Complications may harm the baby or cause its death.
What are the treatments for the condition? Treatment varies depending on:
the amount of bleeding
the age of the foetus
the well-being of the foetus
whether the condition is complete or partial
the position of the foetus
the mother's well-being
whether labour has begun
In asymptomatic or mild cases, bed rest and no sexual intercourse may be advised. As the uterus grows, the placenta may move to a safer position. Other treatment may include:
using foetal monitors as needed
giving the mother fluids through a vein
monitoring the mother's vital signs, such as blood pressure, heart rate, and urine output
observing, but not interfering with, the pregnancy if tests and signs suggest mother and foetus are fine
giving the mother blood transfusions to replace lost blood if the foetus is immature, not in distress, and younger than 36 weeks old
allowing a vaginal birth if the mother and foetus are stable
Once a foetus is 36 weeks old, a caesarean section is generally done to avoid potential complications for mother and baby. First, though, tests may be done to check foetal maturity.
What are the side effects of the treatments? The treatments for this condition may be lifesaving. Possible side effects should be weighed against the loss of life. Any surgery can cause bleeding and infection. Blood transfusions and medications can cause allergic reactions.
What happens after treatment for the condition? After the birth, the woman will be watched closely for signs of continued bleeding through:
How is the condition monitored? A woman will be closely monitored throughout pregnancy to determine the status of the foetus, as well as her own health.
Author: Eva Martin, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
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