A miscarriage is the loss of a pregnancy that happens sometime during the first 23 weeks. Around three quarters of miscarriages happen during the first 12 weeks of pregnancy (the first trimester).

The main symptom of a miscarriage is vaginal bleeding, which may be followed by cramping and pain in your lower abdomen. If you have vaginal bleeding, contact your maternity team or early pregnancy unit at your local hospital straight away.

Read more about the symptoms of miscarriage.

While a miscarriage does not usually seriously affect a woman’s physical health, it can have a significant emotional impact. Many couples experience feelings of loss and grief.

You may also need treatment to remove any tissue that left in your womb. Read more about treating miscarriage.

For most women, a miscarriage is a one-off event and they go on to have a successful pregnancy in the future.

What causes a miscarriage?

It is thought that two thirds of early miscarriages are due to abnormal chromosomes in the baby. Chromosomes are genetic "building blocks" that guide the development of a baby. If a baby has too many or not enough chromosomes, the pregnancy can end in miscarriage.

In later miscarriages, a problem with the womb or cervix (neck of the womb) may be the cause. 

Read more about what causes a miscarriage.

How common are miscarriages?

Miscarriages are much more common than most people realise. This may be because many women who have had a miscarriage prefer not to talk about it.

Among women who know they are pregnant, it is estimated that 12% of these pregnancies will end in miscarriage. This is around one in eight pregnancies. Many more miscarriages occur before a woman is even aware that she has become pregnant.

Losing three or more pregnancies in a row (recurrent miscarriages) is uncommon and affects around 1 in 100 women. Even in cases of recurrent miscarriages, an estimated three quarters of women go on to have a successful pregnancy in the future. 

The most common symptom of miscarriage is vaginal bleeding. This can vary from light spotting or brownish discharge, to heavy bleeding and bright red blood. The bleeding may come and go over several days.

Light vaginal bleeding is common during the first trimester of pregnancy (the first 12 weeks), so having this symptom does not necessarily mean that you have had a miscarriage. However, if you have vaginal bleeding, contact your maternity team or early pregnancy unit at your local hospital straight away.

Other symptoms

Other symptoms of a miscarriage include:

• cramping and pain in your lower abdomen
• a discharge of fluid from your vagina
• a discharge of tissue from your vagina
• no longer experiencing the symptoms of pregnancy, such as feeling sick and breast tenderness 

When to seek urgent medical help

On rare occasions, miscarriages happen because the pregnancy develops outside the womb. This is known as an ectopic pregnancy. Ectopic pregnancies are potentially serious because there is a risk that you could experience internal bleeding.

Symptoms of an ectopic pregnancy include:

• heavy vaginal bleeding (soaking more than one sanitary pad every hour)
• persistent and severe abdominal pain
• pain in your shoulder tip
• feeling very faint and light-headed, and possibly fainting

Symptoms of an ectopic pregnancy usually appear between weeks 5-14 of the pregnancy.

If you experience any of the symptoms above, visit your nearest accident and emergency (A&E) department immediately. If you are unable to travel, you can call up and get advice from NHS Direct Wales on 0845 4647.

Read more about ectopic pregnancies.

Molar pregnancies

Vaginal bleeding can also be caused by a molar pregnancy. This is a pregnancy that has not developed normally, resulting in a mass of abnormal cells within the womb instead of a baby. A molar pregnancy is usually identified during the first ultrasound scan, at 10-16 weeks of pregnancy.

Read more about molar pregnancies.

If a miscarriage happens during the first trimester of pregnancy (the first three months), it is usually due to problems with the unborn baby (foetus).

If a miscarriage happens during the second trimester of pregnancy (between weeks 14 and 26), it is usually the result of an underlying health condition in the mother.

First trimester miscarriages

Most first trimester miscarriages are caused by problems with the chromosomes of the foetus.

Chromosome problems

Chromosomes are blocks of DNA. They contain a detailed set of instructions that control a wide range of factors, from how the cells of the body develop to what colour eyes a baby will have.

For a pregnancy to be successful, a foetus needs to have 46 chromosomes in total:

• 23 are from the father’s sperm
• 23 are from the mother’s egg

Sometimes, something can go wrong at the point of conception and the foetus receives too many or not enough chromosomes. The reasons for this are often unclear, but it means that the foetus will not be able to develop normally, resulting in a miscarriage.

It is estimated that up to two thirds of early miscarriages are associated with chromosome abnormalities. 

Placental problems

The placenta is the organ that links the mother’s blood supply to her baby’s. If there is a problem with the development of the placenta it can also lead to a miscarriage.

Risk factors

An early miscarriage may happen by chance. However, there are several known risk factors which increase the chances of problems occurring.

Age

One of the most important risk factor for miscarriage is the age of the mother:

• In women under 30, 1 in 10 pregnancies will end in miscarriage.
• In women aged 35-39, up to 2 in 10 pregnancies will end in miscarriage.
• In women over 45, more than half of all pregnancies will end in miscarriage.

Other risk factors

Other risk factors for having a miscarriage include:

• obesity 
• smoking during pregnancy
• drug misuse during pregnancy (particularly cocaine)
• drinking more than 200mg of caffeine a day: one mug of tea contains around 75mg of caffeine, and one mug of instant coffee contains around 100mg of caffeine
• drinking more than two units of alcohol a week: one unit is half a pint of bitter or ordinary strength lager, a small glass of wine or a 25ml measure of spirits

Second trimester miscarriages

Long-term health conditions

There are several long-term (chronic) health conditions that can increase the risk of having a miscarriage. These are:

• diabetes (if it is poorly controlled)
• severe high blood pressure (hypertension)
• lupus (a condition where the immune system attacks healthy tissue)
• kidney disease 
• an overactive thyroid gland (hyperthyroidism)
• an underactive thyroid gland (hypothyroidism)
• coeliac disease (a condition that affects the digestive system) 

Infections

There are some infections that may increase the risk of having a miscarriage. These include:

• rubella (German measles)
• cytomegalovirus
• toxoplasmosis (a bacterial infection)
• a bacterial infection of the vagina called bacterial vaginosis
• HIV
• sexually transmitted infection such as chlamydia, gonorrhoea and syphilis 
• malaria (a tropical disease spread by mosquitoes)

Medicines

Some medicines can also increase the risk of miscarriage:

• misoprostol (used for conditions such as rheumatoid arthritis)
• retinoids (used for eczema and acne)
• methotrexate (used for conditions such as rheumatoid arthritis)
• non-steroidal anti-inflammatory drugs (used for pain and inflammation)

To be sure that a medicine is safe in pregnancy, always check with your doctor, midwife or pharmacist before taking it.

Antibodies

Antibodies are proteins that are produced by the immune system (the body’s natural defence system) to fight infection.

Some women who have had three or more miscarriages in a row (recurrent miscarriages) have a higher than usual level of an antibody called antiphospholipid (aPL) in their blood. The aPL antibodies are known to cause blood clots. These blood clots can block the supply of blood to the foetus, which can cause a miscarriage.

Having a high number of aPL antibodies in your blood is known as Hughes syndrome. Read more about Hughes syndrome.

Womb structure

Problems and abnormalities with the womb can also lead to second trimester miscarriages. Possible problems with the structure of the womb include:

• non-cancerous growths in the womb called fibroids
• scarring on the surface of the womb

Weakened cervix

In some cases, the muscles of the cervix (neck of the womb) are weaker than usual. This is known as a weakened cervix or cervical incompetence. A weakened cervix may be due to a previous injury to this area, or may have been something you were born with. 

The muscle weakness can cause the cervix to open too early during pregnancy, leading to a miscarriage.

Hyperprolactinaemia

Prolactin is a hormone which is produced during pregnancy. Prolactin helps to prepare the breasts for breastfeeding. Sometimes, women have a higher level of prolactin in their body than usual. This is known as hyperprolactinaemia.

Some limited evidence suggests that hyperprolactinaemia may be linked to an increased risk of miscarriage.

Polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a condition where the ovaries are larger than normal. It can lead to hormonal imbalances inside the womb.

Polycystic ovary syndrome is known to be a leading cause of infertility. There is some evidence to suggest that it may also be linked to an increased risk of miscarriage in women who are still fertile. However, the exact role that polycystic ovary syndrome plays in miscarriages is unclear.

Read more about polycystic ovary syndrome.

Misconceptions about miscarriage

There are a number of widely held assumptions about the possible causes of miscarriages. However, there is no evidence to support such claims.

An increased risk of miscarriage is not linked to:

• a mother’s emotional state during pregnancy, such as being stressed or depressed
• having a shock or fright during pregnancy
• exercise during pregnancy (but discuss what type of exercise is suitable for you during pregnancy with your GP or midwife)
• lifting or straining during pregnancy
• working during pregnancy
• having sex during pregnancy

If you see your GP or midwife because of vaginal bleeding or other symptoms of miscarriage, you may be referred to an early pregnancy unit at a hospital for tests. 

Tests

The hospital can do tests to confirm whether your pregnancy has ended and you have had a miscarriage. The tests can also confirm whether:

• There is still some foetal tissue left in your womb (an incomplete miscarriage).
• All the foetal tissue has been passed out of your womb (a complete miscarriage). 

The tests include:

• blood tests to measure hormones associated with pregnancy, such as beta-human chorionic gonadotropin (hCG) and progesterone
• a transvaginal (through the vagina) ultrasound scan: a small probe, known as a transducer, is inserted into your vagina to take a close-up image of your womb; the procedure can feel a little uncomfortable but is not painful
• a pelvic examination

Recurrent miscarriages

If you have had three or more miscarriages in a row (recurrent miscarriages), further tests can check if there is an underlying cause. However, in around half of couples no cause is found. These further tests are outlined below. Some of these can only be used if you become pregnant again.

Karyotyping

If you have had recurrent miscarriages, you and your partner can be tested for abnormalities in your chromosomes (blocks of DNA) that could be causing the problem. This is known as karyotyping.

If karyotyping detects problems with your or your partner’s chromosomes, you can be referred to a clinical geneticist (gene expert). They will be able to explain your chances of a successful pregnancy in the future and whether there are any fertility treatments, such as in vitro fertilisation (IVF), that you could try. This type of advice is known as genetic counselling.

Read more about genetic testing and counselling. 

Ultrasound scans

A pelvic ultrasound can be used to check the structure of your womb for any abnormalities. The procedure involves using an ultrasound scanner to study your lower abdomen and pelvis.

A transvaginal ultrasound can check if you have a weakened cervix. This test can usually only be carried out if you become pregnant again.

Blood testing

Your blood can be checked for high levels of:

• the hormone prolactin
• the antiphospholipid (aPL) antibody

Prolactin testing can only happen if you become pregnant again.

A miscarriage can have a profound emotional impact, not only on the woman herself but also on her partner, friends and family.

Emotional impact

Sometimes, the emotional impact is felt immediately after the miscarriage, whereas in other cases it can take several weeks.

The most common emotions that are felt after a miscarriage are grief and bereavement.

Physical symptoms of grief and bereavement include:

• fatigue (tiredness)
• loss of appetite
• difficulties concentrating
• sleeping problems

Emotional symptoms of grief and bereavement include:

• guilt
• shock and numbness
• anger (sometimes at a partner, or at friends or family members who have had successful pregnancies)
• an overwhelming sense of sadness

Different people grieve in different ways. Some people find it comforting to talk about their feelings while others find the subject too painful to discuss.

Some women come to terms with their grief after a few weeks of having a miscarriage and start planning for their next pregnancy. For other women, the thought of planning another pregnancy is too traumatic, at least in the short term.

Miscarriage can also cause feelings of anxiety or depression, and can lead to relationship problems.

Getting support

If you are worried that you or your partner are having problems coping with grief, you may need further treatment and counselling. There are support groups that can provide or arrange counselling for people who have been affected by miscarriage.

Read more about counselling. You can also find bereavement support services in your area.

Your GP can provide you with support and advice and the following organisations can also help:

• The Miscarriage Association is a charity that offers support to people who have lost a baby. They have a helpline 01924 200 799 (Monday to Friday, 9am to 4pm) and an email address info@miscarriageassociation.org.uk and can put you in touch with a support volunteer.
• Cruse Bereavement Care helps people understand their grief and cope with their loss. They have a helpline 0844 477 9400 (Monday to Friday, 9am to 5pm) and a network of local branches where you can find support. 

Even if you take the best care of yourself during pregnancy, you often can't prevent a miscarriage.

However, there are ways to lower your risk of miscarriage:

• Do not smoke during pregnancy – see NHS Smokefree for more information about smoking and pregnancy. 
• Do not drink alcohol during pregnancy.
• Do not use illegal drugs during pregnancy.
• Drink at least 1.2 litres (six to eight glasses) of fluids, such as water and fruit juice, every day.
• Eat a healthy, balanced diet with at least five portions of fruit and vegetables a day.

Your weight

Obesity increases your risk of miscarriage. A person is obese when they have a body mass index (BMI) of over 30. You can check your BMI using the healthy weight calculator. However, if you are pregnant the calculator may not be accurate, so you should consult your midwife or doctor instead. 

The best way to protect your health and your baby’s wellbeing is to lose weight before you become pregnant. By reaching a healthy weight, you cut your risk of all the problems that are associated with obesity in pregnancy. Contact your GP for advice about how to lose weight. They may be able to refer you to a specialist weight-loss clinic.

As yet, there is no evidence to suggest that losing weight during pregnancy will lower your risk of miscarriage, but eating healthily and activities such as walking and swimming are good for all pregnant women. If you were not active before becoming pregnant, you should consult your midwife or doctor before starting a new exercise regime while you are pregnant.