Pregnancy bleeding after 24: what's causing it and what to do

"If you're bleeding heavily and/or in severe pain, call 999. Otherwise, ring your hospital, and the midwife on duty will ask you questions about the nature and extent of your bleeding and then advise you whether to come in or not."

What are the chances of bleeding in late pregnancy being serious?

About a quarter of cases of antepartum haemorrhage – the medical term for bleeding after the 24th week of pregnancy – are caused by 1 of 2 potentially serious conditions: placenta praevia, and placental abruption.

Other, more minor, causes include inflammation of, or growths (polyps), on your cervix (the neck of your womb) or an infection in your cervix or vagina.

And the most common cause – particularly late in your 3rd trimester – is a 'bloody show', when the plug of mucus that seals your womb comes away, mixed with small amount of blood, signalling the start of labour. This is generally only considered serious if you're not yet 36 weeks pregnant.

Why I am bleeding?

There are various possible causes of bleeding in late pregnancy, ranging from the minor to the more serious. Here's a rundown of what it could be...

It could be… cervical erosion

This is a lot less serious than it sounds. Cervical erosion, sometimes called cervical ectropion or ectopy, is the medical term for when the blood supply to your womb and cervix is increased, as a result of your pregnancy. As these cells are soft, they can bleed more easily (though harmlessly and painlessly). This can result in spotting or light bleeding – either for no apparent reason or after sex.

It could be… an infection

Any infection of your vagina or cervix (including sexually transmitted diseases, such as genital herpes, chlamydia or gonorrhoea) can cause bleeding. (And will, obviously, need to be treated.)

It could be... a vaginal polyp

A polyp is a harmless growth. And if it's in your vagina, it can cause harmless bleeding at any stage in your pregnancy.

It could be... the start of labour

For some women, labour starts with the loss of the mucus plug that's been sealing off their womb. This 'blob' of mucus is often mixed with blood, as some very small veins in your cervix may also be torn as this happens. Usually, the amount of blood you see is small and looks old – and, unless you're less than 36 weeks pregnant, your midwife may advise you to stay at home until labour starts. "But if there's more blood than that," says Patrick O'Brien, "and if there is some fresh, red bleeding – more than a teaspoon or 2 – then you'll need to be seen more urgently."

It could be… placenta praevia

This is when your placenta has become attaches in the lower part of your womb, sometimes completely covering your cervix (the neck of your womb, through which your baby must pass to be born). It happens in about 1 in 200 pregnancies (more commonly in twin pregnancies) and can cause heavy, painless bleeding from about 32 weeks. You will be admitted to hospital until the bleeding settles. If the degree of your placenta praevia is minor, you may be allowed home until your doctors decide to induce labour but, more often, you'll need to stay in hospital and your baby will be born by C-section.

It could be… placenta accreta

This is a rare but serious condition when your placenta has become stuck to the muscle of your womb and/or to nearby structures, such as your bladder. This is more common if you have previously had a C-section. It can cause heavy bleeding, either in the 3rd trimester or when you give birth.

It could be... vasa praevia

Vasa praevia is the medical term for when the blood vessels that provide blood to your baby (through the umbilical cord) grow across or near to your cervix. It's very rare – and the bleeding usually only starts when your waters break.

It could be... placental abruption

This is a serious condition where your placenta starts to come away from the wall of your womb. This can happen very suddenly and the bleeding is usually severe – although it can only or mostly be internal bleeding, so you may not notice any or much blood yourself. Typically, though, you will feel sudden and severe abdominal pain. Placental abruption can be life-threatening – for both you and your baby – and requires urgent treatment. In most cases, your baby will be delivered by emergency C-section.

What should I do if I’m bleeding in late pregnancy?

As we've stressed above, if you have any bleeding after 24 weeks of pregnancy, you need to call your midwife or your hospital maternity unit straightaway. And if you're bleeding heavily or in pain, you should call 999.

It's possible that your bleeding isn't a sign of anything really serious – particularly if you're just spotting and not in pain – but, as some of the causes of late-pregnancy bleeding aren't obvious but need urgent intervention, it's important that you seek medical advice as soon as possible.

About our expert: Patrick O'Brien

Patrick O'Brien has been a Consultant & Honorary Senior Lecturer in Obstetrics and Gynaecology at University College London Hospitals since 1999. He is also the Divisional Clinical Director for Women's Health. He specialises in Maternal Medicine and high-risk obstetrics and has a particular interest in medical complications of pregnancy.