Bleeding during pregnancy - causes before and after 12 weeks

When should you worry about bleeding during pregnancy?

A pregnant woman in a dressing gown touches her baby bump and looks worried about bleeding during pregnancy
(Image credit: Getty/Future)

Bleeding during pregnancy, whether in the first 12 weeks or later on in pregnancy, can be very distressing. However, it can also be fairly common and most women who experience signs will go on to have healthy babies.

Causes and risks for bleeding depend on how far along you are in your pregnancy. Miscarriage (opens in new tab), ectopic pregnancy (opens in new tab), and infections, as well as problems with your placenta, are all reasons for bleeding that require immediate medical assistance. If you do experience bleeding during pregnancy, always seek advice from a healthcare professional. All bleeding or spotting in pregnancy should be investigated, to ensure the health of both you and your baby.

Registered Midwife Avril Flynn (opens in new tab), says, “If you experience bleeding in your pregnancy, speak to your maternity assessment unit. They can ask you a series of questions to triage you and work out the best professional for you to see, depending on what they suspect is wrong and how many weeks pregnant you are. Use reputable, trusted websites for information and advice, and beware of social media when you’re worried. Reading others’ stories could either give you false hope or dissuade you from seeking help when you need it. No one but a healthcare professional can tell you why you’re bleeding.” 

Bleeding during pregnancy before 12 weeks

There is a range of reasons for bleeding in early pregnancy. While some do sadly mean your pregnancy has come to an end, not all bleeding ends in loss. 

Early bleeding during pregnancy causes range from implantation bleeding, right through to various causes of miscarriage. Bleeding in early pregnancy is quite common; research (opens in new tab) suggests that around 1 in 3 pregnancies have some form of bleeding. 

Avril Flynn explains,  “Bleeding in early pregnancy is not always indicative of miscarriage, but it can be. Most people that bleed during pregnancy go on to have healthy pregnancies that those who don’t. If you have any bleeding or spotting, always talk to a healthcare professional. They will ask you how much blood there is and whether you also have other symptoms.”

Implantation bleeding

Implantation is often discussed online on social media groups and given as a reason for bleeding in the first few weeks of early pregnancy before you know you are pregnant. However, it is a controversial subject, which is disputed by medical professionals. 

Despite the lack of evidence for it, the NHS refers (opens in new tab) to implantation bleeding and defines it as spotting around the time you would have normally expected your period to start. 

What is implantation?

After an egg and a sperm meet, the newly created form is called a “zygote” and it must implant into the uterus for the pregnancy to develop and progress into an embryo. In some early pregnancies, this process does not happen properly. According to research (opens in new tab), up to two-thirds of pregnancies do not continue “because of implantation failure”.

Based on an idea first described in 1954 (opens in new tab), implantation bleeding is theorised to happen when the zygote “burrows” into the womb, disrupting blood vessels in the uterine lining.

However, there is very little current research on implantation bleeding. Some studies (opens in new tab) have found no evidence for it at all. These studies are small and most research only looks at bleeding in groups of weeks (trimesters). 

Cervical changes

Your cervix (the neck of the womb) undergoes many changes throughout all stages of pregnancy, which can make it more sensitive. This sensitivity can mean that anything that comes into contact with your cervix could prompt a little bleeding. Transvaginal ultrasound scans, done in the earliest weeks of pregnancy (when an ultrasound probe is inserted into your vagina) can sometimes cause a bit of bleeding or spotting. You might also experience bleeding during pregnancy caused by cervical changes after having sex.

Medical research (opens in new tab) suggests that a complex mixture of hormones, enzymes, and proteins are involved in these cervical changes. Registered midwife Avril Flynn says “cervical changes can be a cause for early bleeding during pregnancy but it’s often hard to diagnose. Sometimes no cause for your bleeding will be identified. That can be really frustrating but all we can do is rule out the most concerning causes.”

Infection

Any kind of infection in your womb, cervix, or vagina could be a cause of early bleeding during pregnancy. This includes sexually transmitted infections (STIs) such as herpes, chlamydia, or gonnorhea. While most women will undergo some screening for STIs at their booking appointment, if you have not yet “booked in” your pregnancy (recommended around 8-10 weeks of pregnancy) you will not yet have had these tests. If you are worried you could have an STI, contact your GP or midwife as soon as you can. This will prevent it from causing issues in your pregnancy.

Source: NHS patient information on STIs  (opens in new tab)

Ectopic pregnancy

Ectopic pregnancy, where a pregnancy starts to develop within a fallopian tube (instead of the uterus) can be a serious and life-threatening cause of early bleeding in pregnancy. Though it is uncommon (studies (opens in new tab) indicate it occurs in 1-2 percent of naturally conceived pregnancies), if you suspect an ectopic pregnancy, seek urgent medical assistance. 

Signs and symptoms of ectopic pregnancy are a positive pregnancy test, accompanied by any of the following:

  • Pain in the lower abdomen (above your pubic bone) usually on just one side.
  • Pain felt in the shoulder (referred pain).
  • Vaginal bleeding or spotting.
  • Feeling sick or dizzy accompanied by vaginal bleeding.

You will usually be referred for an assessment by an expert in early pregnancy and advised to have an ultrasound to locate the pregnancy. This is the only way to confirm the location of the pregnancy. 

Unfortunately, an ectopic pregnancy is not viable. If your pregnancy is not developing within the uterus, you cannot carry the baby to term. There are a few options for treating ectopic pregnancy, depending on how quickly it is diagnosed and whether there is an immediate risk to your health. You may be prescribed drugs or, in some cases, need surgery.

Miscarriage

Sometimes bleeding in pregnancy will mean that you are losing your pregnancy (miscarrying). Miscarriage is estimated to affect 25% of pregnancies, according to the UK Charity Tommy’s (opens in new tab)

The bleeding during pregnancy that is experienced when you miscarry can vary from light to heavy. It might be dark red and contain clots. It can come and go over days and possibly even last for a few weeks. It is different for everyone and there isn’t a “normal” amount as it depends on your body and how far along your pregnancy is.

Miscarriage can be painful or uncomfortable and studies (opens in new tab) suggest that cramping and/or pain with bleeding is an indicator of miscarriage.

Support for miscarriage

It’s not always clear why miscarriage happens, but the most important thing to know is that it is not your fault. Miscarriage can be a devastating experience - for you and your partner. 

If you suspect you are miscarrying, speak to a healthcare professional for more information. Natural miscarriage (not prompted by medication) might sometimes not complete (some tissue may remain in your womb) and you will need to know how to ensure you are physically healthy. Sometimes, if you do not know you are pregnant with twins or triplets, you might be losing one pregnancy and still be pregnant. It’s important to seek help and confirmation from a medical professional.

Support for the grief around miscarriage is available from your GP and the Miscarriage Association has a range of resources (opens in new tab) available to help you understand what has happened.

Molar pregnancy

A molar pregnancy (hydatidiform mole) is when a fertilised egg and placenta develop abnormally. It will always result in a miscarriage, which will cause bleeding in early pregnancy. There are two types of molar pregnancy: partial and complete. Neither of these types of molar pregnancies can develop into a normal embryo.

Molar pregnancy as a cause of early bleeding in pregnancy is rare. Research (opens in new tab) estimates molar pregnancy occurs in 60-120 of 100,000 pregnancies. 

Bleeding during pregnancy from a molar pregnancy can range from dark brown or bright red. The medical literature (opens in new tab) describes bleeding from molar pregnancy as resembling prune juice and says some patients lose “grape-like” clusters of tissue from the vagina.

There may be other signs, such as a uterus that is larger than expected for your stage of gestation. Another key sign of a molar pregnancy is severe pregnancy sickness (hyperemesis gravidarum (opens in new tab)), due to the very high levels of pregnancy hormone (HCG) that molar pregnancies prompt. 

What happens if you have a molar pregnancy?

If you are diagnosed with a molar pregnancy, you might need medication or surgery to help your body complete the miscarriage. Some patients won’t need any treatment if they have miscarried naturally.

After you recover from your molar pregnancy, you will be monitored closely as there can be future complications. Some of those diagnosed with molar pregnancies will go on to develop cancer, but this is rare.

If you want to try to conceive again after a molar pregnancy, you will be advised to wait for some time. The recommended waiting time period will vary according to your circumstances, so follow the advice of your healthcare team.

Support for your loss is available from the Miscarriage Association. (opens in new tab)

Subchorionic Haematoma (SCH)

A subchorionic haematoma (SCH) is the most common cause (opens in new tab) of early bleeding in pregnancy between 11-20 weeks. It is a bleed caused by a slight detachment of the placenta from where it is attached to the uterine wall.

Bleeding during pregnancy from SCH can range from light to bright red, through to light brown, depending on how recent the bleeding was.

Although it does not always mean a miscarriage, it will be monitored closely at scans. 

Midwife Avril Flynn  told us, “In the foetal sac, there are two layers; amnion and chorion, plus the placenta. Between the amnionic and chorionic layers, you can have a bleed, which is probably from the placenta. Depending on the size and position, generally, there is nothing that can be done about the bleed. Sometimes it can mean your placenta is abnormally attached. A particularly large SCH would be a concern. Your healthcare team will monitor you and hopefully, it won’t get bigger. If it does, it could cause a miscarriage. In many cases, it will be reabsorbed and there won’t be any longer-term issues."

Evidence is mixed on the effect of SCHs on the outcome of pregnancies. Recent studies indicate they are not associated with future risks for your pregnancy if they resolve early.

Bleeding during pregnancy after 12 weeks

Some of the causes of bleeding in pregnancy after 12 weeks (first trimester) will be the same as causes of bleeding that happen before 12 weeks. However, when you enter the second trimester, there can be bleeding caused by problems with the formation of the placenta. These include placental abruption (where the placenta detaches from the wall of the uterus) and placenta previa (where the placenta covers the cervix). 

Low-lying placenta (Placenta previa) and vasa prevue

One cause of bleeding in late pregnancy is a low-lying placenta (when your placenta develops too close to your cervix or covers it). This is called placenta previa. 

In most cases, (9 out of 10 (opens in new tab) women, according to the NHS), the placenta will have moved away from the cervix by 32 weeks. Usually diagnosed by ultrasound at the 18-20 week anomaly scan, you will be monitored and if the placenta remains too close to the cervix, a caesarean birth will be necessary. Medical literature (opens in new tab) describes placenta previa as affecting 0.3% to 2% of pregnancies. 

A similar condition causing bleeding in late pregnancy; vasa previa, is when some of the blood vessels between the umbilical cord and the placenta cover your cervix. This is very rare and is estimated (opens in new tab) to occur in 1 in 2500 to 1 in 5000 pregnancies.

If you go into labour and have placenta previa or vasa previa, you will experience very severe bleeding and it is an emergency situation. If you have been diagnosed with either of these pregnancy complications and experience any signs of labour (opens in new tab), call 999 and seek immediate emergency assistance.

Placental abruption

Placental abruption causes bleeding in pregnancy and happens when the placenta comes away from the uterine wall before the baby has been born (in the second stage of labour (opens in new tab)). It is an emergency situation and the Royal College of Obstetricians and Gynaecologists (RCOG (opens in new tab)) says it is the “cause of up to 50% of the estimated 500, 000 maternal deaths that occur globally each year”. 

However, it is rare and affects just 0.3-1 percent (opens in new tab)of pregnancies.
Placental abruption can be classified (opens in new tab) as mild, moderate, or severe (depending on whether it is partial or complete) and it will not always mean that your pregnancy ends before it should. Some women with a mild, partial placental abruption can continue their pregnancy with monitoring. 

Signs of placental abruption, along with bleeding during pregnancy, are:

  • Intense, sudden pain
  • Firm uterus (described in the literature as a “board-like” tone)

A ‘show’ (Premature labour)

If you go into labour before 37 weeks, this is known as premature labour. This is sometimes accompanied by loss of your mucus plug. This is sometimes referred to as “a show” or “bloody show” because it can be streaked with blood. The blood within the mucus will be light pink or red. A show does not always mean labour is near, however. You can lose your mucus plug weeks before labour starts and your body will just make more mucus to replace what you have lost.

A bloody show, accompanied by other signs of labour (opens in new tab), like strong contractions (opens in new tab), before 37 weeks is cause for concern. If you lose your mucus plug and you have bleeding, do seek immediate advice from your maternity assessment unit. The number for your local unit should be on your pregnancy notes, or you can search online.

What’s the difference between bleeding and spotting?

The sight of any blood when you are pregnant can be alarming. A healthcare professional might ask you how much blood you are losing and ask if it is “spotting”. The difference between spotting and bleeding isn’t always immediately obvious. Thinking about how you are managing the blood can be a helpful way to distinguish what you’re experiencing. If you only see blood when you wipe yourself in the toilet, this is usually described as spotting. The same is true when there are just a few spots seen on a pad or your underwear. 

Bleeding is a little more sustained and you will probably need a pad. Heavy bleeding means you will have to change your pad often.

Midwife Avril Flynn told us, “Spotting is dots of blood or brown staining, whereas bleeding will mean you need a panty liner. Sometimes it’s useful to save pads or underwear to show healthcare professionals what you’ve been experiencing. If you have clots then tell your midwife or doctor about those too. Describe how many you’ve seen and the sort of size they were.

When should I seek help for bleeding during pregnancy?

Although bleeding during pregnancy is not always a cause for concern, you won’t know unless you are checked by a medical professional. The fear of the unknown might be worse than the reality of why you are bleeding. However, as there are some reasons for bleeding during pregnancy that are dangerous for you and the pregnancy, all bleeding must be investigated. 

The cause for your bleeding might not always be determined and this can be worrying and frustrating. If you feel that your concerns are not being listened to, remember that you have the right to ask for a second opinion.

Avril Flynn, Registered Midwife, told us, “The cause for your bleeding needs to be determined, whatever stage of pregnancy you are at. We can use a range of medical tests to check how you and your baby are. These range from blood tests to check the level of HCG (pregnancy hormone detected by pregnancy tests) to ultrasound scans to see how the baby is growing. HCG blood tests always need to be taken in pairs, 48 hours apart. A single blood test will not tell you how the pregnancy is progressing. Never feel embarrassed or you’re wasting someone’s time if you need to seek help for bleeding in pregnancy. It’s our job to make sure you - and your pregnancy - are OK. Always get checked. Even if you’ve already had a bleed and then have another one, have it checked out.”

If your bleeding is accompanied by dizziness or you have fainted, call an ambulance. Don’t use public transport or be tempted to drive yourself. 

Bleeding during pregnancy is scary and will always worry anyone, so if you’re experiencing anxiety about your situation, don’t be afraid to approach your midwife for support. They are experienced in helping women who have experienced bleeding in pregnancy and will be able to provide reassurance and advice specific to you.

Further information about bleeding during pregnancy-related to miscarriage is available from the Miscarriage Association.