Complications that can affect the placenta during pregnancy or childbirth include:
- low-lying placenta and placenta praevia
- retained placenta – when part of the placenta remains in the womb after giving birth
- placental abruption – when the placenta starts to come away from the wall of the womb
These complications aren't common.
Low-lying placenta and placenta praevia
As your pregnancy progresses, your womb expands and this affects the placenta's position. The area where the placenta is attached usually stretches upwards, away from your cervix.
If the placenta stays low in your womb, near to or covering your cervix, it may block the baby's way out.
This is called low-lying placenta if the placenta is less than 2cm from the cervix, or placenta praevia if the placenta is completely covering the cervix.
Placenta praevia, where the cervix is completely covered at the end of pregnancy, affects about 1 in every 200 births.
The position of your placenta will be recorded at your 18- to 21-week ultrasound scan.
If your placenta is significantly low, you'll be offered an extra ultrasound scan later in your pregnancy (usually at about 32 weeks) to check its position again.
For 9 in every 10 women, the placenta will have moved into the upper part of the womb by this point.
If the placenta is still low in your womb, there's a higher chance that you could bleed during your pregnancy or during your baby's birth. This bleeding can be very heavy and put you and your baby at risk.
You may be advised to come into hospital at the end of your pregnancy so emergency treatment (such as a blood transfusion) can be given very quickly if you bleed.
If the placenta is near or covering the cervix, your baby can't be delivered through the vagina, so a caesarean section will be recommended.
A low-lying placenta can be associated with painless, bright red bleeding from the vagina during the last 3 months of pregnancy. If this happens to you, contact your midwife or GP immediately.
Retained placenta
After your baby's born, part of the placenta or membranes can remain in the womb. This is known as retained placenta. If untreated, a retained placenta can cause life-threatening bleeding.
Breastfeeding your baby as soon as possible after the birth can help your womb contract and push the placenta out.
Your midwife may also ask you to change your position (for example, by moving to a sitting or squatting position). In some cases, you may be given an injection of a medicine to help your womb contract.
If these methods don't work, a doctor may need to remove the placenta by hand. This can be painful, so you'll be given an anaesthetic.
Placental abruption
Placental abruption is a serious condition in which the placenta starts to come away from the inside of the womb wall.
It can cause stomach pain, bleeding from the vagina and frequent contractions.
It can also affect the baby, increasing the risk of premature birth, growth problems and stillbirth.
It's not clear what causes placental abruption, but factors that increase the risk include injury to the abdominal area, smoking, cocaine use and high blood pressure.
If you're near your due date, the baby will need to be born straight away and a caesarean section may be recommended.
But if the baby's very premature and the abruption is minor, you may be kept in hospital for close observation.
Always speak to your midwife or GP if you're concerned about any aspect of your health when you're pregnant. You can also call NHS 111.