What is placenta praevia?

What is placenta praevia?
The placenta is your baby's source of nourishment through pregnancy. Sometimes, it grows low down in the womb and can cover the entrance to the uterus (the cervical os). Obviously this is a problem because it is blocking the baby's route out of your body at birth, but also, as your due date approaches, the lower part of the womb stretches and this can cause the placenta to bleed as it pulls away.
A complete placenta praevia is when the placenta completely covers the cervix. A partial previa means it is partly covered, and a marginal praevia means that the placenta is very close to the cervix.
If the praevia is identified early in a pregnancy, a 'watch and wait' policy is usually advised, because the placenta may well move up and no longer be a concern by your due date. Only ten per cent of women who are found to have a low-lying placenta at an early scan go on to encounter placenta praevia.

Why is placenta praevia a concern?
It can cause some developmental problems for the baby, and the biggest worry for the mother and baby is excessive bleeding.
Partial or complete praevia usually means that a woman will have to have a caesarian section and possibly a blood transfusion. This is quite common and can save lives. If there is a marginal praevia, it is possible that the doctor might allow a vaginal birth.

How do you know if you have placenta praevia?
During routine antenatal scans, the position of the placenta will be noted.
Because there is a strong chance the placenta will move up and away from the cervix, an additional scan later in pregnancy can check for this.
The most likely symptoms of placenta praevia are heavy bleeding but without pain during the last trimester, the baby laying in an unusual position, the uterus appearing larger than usual at a given time during the pregnancy.
Spotting in the first two trimesters can also be a sign, but spotting can mean a lot of things which are often harmless, too.

Who is most likely to have placenta praevia?
The condition can happen during any pregnancy, but there are some situations which tend to make it more likely.
If you have had a caesarian section previously, or other surgery which might have left scar tissue in the womb, you may be more prone to the condition. Also, it is more likely to occur if you have had several babies before, or if you are expecting more than one baby. Women who have children later in life are also more at risk.

What can be done about placenta praevia?
There is nothing that can be done to prevent an incidence of placenta praevia, but doctors like to keep a watch and wait policy on the condition when it is discovered early on in a pregnancy, because the placenta usually moves to a less problematic position as the fetus grows.
Some doctors will advise you to take as much bed rest as you can, but nowadays other doctors will simply advise you not to over-exert yourself, while normal daily routines can be continued.
If the praevia looks like it is not going to move and is partial or complete, your doctor will most likely suggest a caesarian and set a date for it ahead of your due date (before you naturally go into labour). Unless you have excessive bleeding ahead of this date, the CS will be set for a date where specialist feels the baby's lungs are fully established. Usually, an elective cs like this would be set for some time after 36 weeks, when a baby has fully developed.
If you are diagnosed with the condition the main concern will be that you get in touch with your midwife or hospital team urgently if you experience any bleeding.
During the birth and afterwards, the health team will be careful to ensure that excessive bleeding or infection do not affect recovery.
In extreme cases, the condition can be fatal, but all health staff dealing with births are well trained to manage a placenta praevia. 99 per cent of women who have the condition come through the birth well, as do their babies.

The Royal College of Obstetricians and Gynaecologists has some detailed advice on its website which is useful if you have been diagnosed with the condition and want to know more.