There are many reasons why a miscarriage may happen, although the cause is often not identified.

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). About three in every four miscarriages happen during this period.

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

These late miscarriages may be caused by an infection around the baby which leads to the bag of waters breaking before any pain or bleeding, In rare cases, they can be caused by the neck of the womb opening too soon.

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.

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.

Things that increase your risk

An early miscarriage may happen by chance. However, there are several things known to increase your risk of problems happening.

The age of the mother has an influence:

• 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 include:

• obesity
• smoking during pregnancy
• drug misuse during pregnancy
• 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

Several long-term (chronic) health conditions can increase your risk of having a miscarriage in the second trimester. These are:

• diabetes (if it is poorly controlled)
• severe high blood pressure
• lupus (a condition where the immune system attacks healthy tissue)
• kidney disease 
• an overactive thyroid gland
• an underactive thyroid gland 
• coeliac disease (having an adverse reaction to gluten) 

Infections

The following infections may also increase your risk:

• rubella (German measles)
• cytomegalovirus
• toxoplasmosis
• bacterial vaginosis
• HIV
• chlamydia
• gonorrhoea 
• syphilis 
• malaria 

Medicines

Medicines increasing your risk include:

• 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.

Read more about medicines during pregnancy.

Womb structure

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

• non-cancerous growths in the womb called fibroids
• an abnormally shaped 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 usually following a surgical procedure.

The muscle weakness can cause the cervix to open too early during pregnancy leading to a 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 it may also be linked to an increased risk of miscarriages in fertile women. However, the exact role polycystic ovary syndrome plays in miscarriages is unclear.

Misconceptions about miscarriage

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 with your GP or midwife what type of exercise is suitable for you during pregnancy)
• 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 carry out tests to confirm whether you are having a miscarriage.

The tests can also confirm whether there is still some pregnancy tissue left in your womb (an incomplete miscarriage) or if all the pregnancy tissue has been passed out of your womb (a complete miscarriage). 

The first test used is usually an ultrasound scan to check the development of your baby and look for a heartbeat. In most cases, this is usually carried out using a small probe inserted into the vagina (transvaginal ultrasound). This can feel a little uncomfortable but is not painful. You may be able to have an external scan through your tummy if you prefer. Neither type of scan is dangerous to the baby and they do not increase your risk of miscarriage.

You may also be offered blood tests to measure hormones associated with pregnancy, such as beta-human chorionic gonadotropin (hCG) and progesterone. These may be repeated after 48 hours if the levels are borderline or it is very early in your pregnancy.

Sometimes, a miscarriage cannot be confirmed immediately using ultrasound or blood testing. For example, a heartbeat may not be noticeable if your baby is at a very early stage of development (less than 6 weeks). If this is the case, you may be advised to have a further ultrasound and/or a pregnancy test again in a week or two.

Recurrent miscarriages

If you have had three or more miscarriages in a row (recurrent miscarriages), further tests are often used to check for any underlying cause. However, no cause is found in about half of cases. These further tests are outlined below.

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 transvaginal ultrasound can be used to check the structure of your womb for any abnormalities. A second procedure using a 3D ultrasound scanner to study your lower abdomen and pelvis may be used to provide a more accurate diagnosis.

The scan can also check if you have a weakened cervix. This test can usually only be carried out when you become pregnant again, in which case you will usually be asked to come for a scan when you are between 10 and 12 weeks pregnant.

Blood testing

Your blood can be checked for high levels of:

• the hormone involved in the development of the egg (called luteinising hormone)
• the antiphospholipid (aPL) antibody and lupus anticoagulant – this test should be done twice, six weeks apart, when you are not pregnant

Antiphospholipid (aPL) antibodies are known to increase the chance of blood clots. These blood clots can block the blood supply to the foetus, which can cause a miscarriage.

A miscarriage is the loss of a pregnancy during the first 23 weeks.

The main sign 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 GP. Most GPs can refer you to an early pregnancy unit at your local hospital straight away if necessary.

However, bear in mind that light vaginal bleeding is relatively common during the first trimester of pregnancy (the first 12 weeks) and does not necessarily mean you are having a miscarriage.

Read more about the symptoms of miscarriage.

What causes a miscarriage?

There are probably many reasons why a miscarriage may happen although the cause is usually not identified. The majority are not caused by anything that the mother has done.

It is thought that most 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, it will not develop properly.

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

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

Read more about what causes a miscarriage.

Can miscarriages be prevented?

The majority of miscarriages can not be prevented. If a woman has suffered from more than three miscarriages then there are some women who can be helped to keep their pregnancy with medication under the care of a specialist.

However, there are some things you can do to reduce the risk of a miscarriage. Avoid smoking, drinking alcohol and using drugs while pregnant. Being a healthy weight before getting pregnant can also help.

Read more about preventing miscarriages.

What happens if you think you may be having a miscarriage?

If you have the symptoms of a miscarriage, you will usually be referred to a hospital for tests. In most cases, an ultrasound scan can determine whether the pregnancy is ongoing or you are having a miscarriage.

When a miscarriage is confirmed, you will need to talk to your doctor or nurse about the options for the management of the end of the pregnancy. In the majority of cases the pregnancy tissue will pass out naturally in a week or two. Sometimes medication to assist the passage of the tissue may be recommended  or you can choose to have minor surgery to remove it if you don’t want to wait.

Read more about diagnosing a miscarriage and what happens if you have a miscarriage.

After a miscarriage

A miscarriage can be an emotionally and physically draining experience. You may have feelings of guilt, shock and anger.

Advice and support is available at this time from hospital counselling services and charity groups. You may also find it beneficial to have a memorial for your lost baby.

You can try for another baby as soon as your symptoms have passed, although you should ensure you are emotionally and physically ready first.

Having a miscarriage does not necessarily mean you will have another if you get pregnant again. Most people are able to have a healthy pregnancy after a miscarriage, even in cases of recurrent miscarriages. 

Read more about what happens after a miscarriage.

In many cases, the cause of a miscarriage is not known and you wouldn’t have been able to prevent it. 

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

• not smoking during pregnancy 
• not drinking alcohol or using illegal drugs during pregnancy
• eating a healthy, balanced diet with at least five portions of fruit and vegetables a day
• making attempts to avoid certain infections during pregnancy, such as rubella
• being a healthy weight before getting pregnant (see below)

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. If you are pregnant, your midwife or doctor may be able to tell you your BMI. 

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 regimen while you are pregnant.

Read more about obesity and pregnancy and exercise in pregnancy.

Treating an identified cause

Sometimes the cause of a miscarriage can be identified. In these cases, it may be possible to have treatment to prevent this causing any more miscarriages. Some treatable causes of miscarriage are outlined below.

Antiphospholipid syndrome

Antiphospholipid syndrome (APS), also known as Hughes syndrome, is a condition that causes blood clots. It can be treated with medication. Research has shown that a combination of aspirin and heparin (a medicine used to prevent blood clots) can improve pregnancy outcomes in women with the condition.

Read more about treating antiphospholipid syndrome.

Weakened cervix

A weakened cervix, also known as cervical incompetence, can be treated with an operation to put a small stitch of strong thread around your cervix to keep it closed. This is usually carried out after the first 12 weeks of your pregnancy, and is removed around week 37.

The Map of Medicine is used by doctors throughout the NHS to determine the best treatment options for their patients. NHS Choices offers everyone in England exclusive and free access to this cutting-edge internet resource, which lets you see exactly what your doctor sees.

The information in the Map has been approved by the UK’s leading clinical experts, is based on the best available clinical evidence, and is continually updated. To take advantage of this unique resource go to:

Map of Medicine: miscarriage

The most common sign 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.

However, light vaginal bleeding is relatively common during the first trimester of pregnancy (the first 12 weeks) and does not necessarily mean you are having a miscarriage.

If you have vaginal bleeding, contact your GP, maternity team or early pregnancy unit at your local hospital as soon as possible.

Find maternity services in your area.

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 you could experience internal bleeding.

Symptoms of an ectopic pregnancy include:

• persistent and severe abdominal pain
• vaginal bleeding or spotting, commonly after the pain has started.
• pain in your shoulder tip
• feeling very faint and light-headed, and possibly fainting

Symptoms of an ectopic pregnancy usually appear between weeks 5 and 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, call 999 and ask for an ambulance.

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

Advice and support is available during this difficult time.

Remembrance 

It is usually possible to arrange a memorial and burial service if you want one. In some hospitals or clinics, it may be possible to arrange a burial within the grounds. You can also arrange to have a burial at home, although you will need to consult your local authority before doing so.

Cremation is an alternative to burial and can be performed at either the hospital or a local crematorium. However, not all crematoriums provide this service and there will not be any ashes for you to scatter afterwards.

Unlike a stillbirth, you do not need to formally register a miscarriage. However, some hospitals can provide a certificate to mark what has happened if you want one.

Emotional impact

Sometimes, the emotional impact is felt immediately after the miscarriage, whereas in other cases it can take several weeks. Many people affected by a miscarriage go through a bereavement period.

It is common to feel tired, lose your appetite and have difficulty sleeping after a miscarriage. You may also feel a sense of guilt, shock, sadness and anger (sometimes at a partner, or at friends or family members who have had successful pregnancies).

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.

The father of the baby may also be affected by the loss. Men sometimes find it harder to express their feelings particularly if they feel their main role is to support the mother and not the other way round. It may help to make sure you openly discuss how both of you feel.

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 dealing with loss and 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.

Having sex and trying for another baby

You should avoid having sex until all of your miscarriage symptoms have gone. Your periods should return within four to six weeks of your miscarriage, although it may take several months to settle into a regular cycle.

If you do not want to get pregnant, you should use contraception immediately. 

If you do want to get pregnant again, you may want to discuss it with your GP or hospital care team. Make sure you are feeling physically and emotionally well before trying for another pregnancy.

The Miscarriage Association has written a leaflet called Thinking about another pregnancy (PDF, 207kb) that you may find helpful. It is important to remember that most miscarriages are a one-off and are followed by a healthy pregnancy.

Although it is not usually possible to prevent a miscarriage, there are some ways you can reduce the risk. See preventing miscarriage for more information and advice.

If there is no pregnancy tissue left in your womb, no treatment is required.

However, if there is still some pregnancy tissue in your womb, your options are:

• wait for the tissue to pass naturally out of your womb (expectant management)
• take medication that will cause the tissue to pass out of your womb (medical management)
• have the tissue surgically removed (surgical management)

The risk of complications is very small for all these options. Discuss them with the doctor in charge of your care.

Expectant management

It is usually recommended you wait 7-14 days after a miscarriage for the tissue to pass out naturally. This is called expectant management. 

If the pain and bleeding have lessened or stopped completely during this time, this may mean the miscarriage has finished. You should be advised to take a home pregnancy test after three weeks.

If the test shows you are still pregnant, you may need to have further tests to make sure you don’t have a molar pregnancy or an ectopic pregnancy.

If the pain and bleeding haven’t started within 7-14 days, or are continuing or getting worse, this could mean the miscarriage hasn’t begun or that it hasn’t finished. In this case you should be offered another scan. Contact your hospital immediately if the bleeding becomes particularly heavy, you develop a high temperature (fever), or you experience severe pain.

After this scan, you may decide to either continue waiting for the miscarriage to occur naturally, or to have drug treatment or surgery. If you choose to continue to wait, your healthcare professional should check your condition again up to 14 days later.

Medication

You may choose to have medication to remove the tissue if you don’t want to wait.

This involves taking tablets that cause the cervix to open, allowing the tissue to pass out. In most cases, you will be offered tablets called pessaries that are inserted directly into your vagina, where they dissolve. However, tablets that you swallow may be available if you prefer. A medication called mifepristone is sometimes used first, followed 48 hours later by a medication called misoprostol.

The effects of misoprostol tablets usually begin within a few hours. You will experience symptoms similar to a heavy period, such as cramping and heavy vaginal bleeding. You may also experience vaginal bleeding for up to three weeks.

You should be advised to take a home pregnancy test three weeks after taking this medication. If the pregnancy test shows you are still pregnant, you may need to have further tests to make sure you don’t have a molar pregnancy or an ectopic pregnancy.

You may be advised to contact your healthcare professional to discuss your options if bleeding hasn’t started within 24 hours of taking the medication.

Surgery

In some cases, surgery is used to remove any remaining pregnancy tissue. You may be advised to have immediate surgery if:

• you experience continuous heavy bleeding
• there is evidence the pregnancy tissue has become infected
• medication or waiting for the tissue to pass out naturally have been unsuccessful

Surgery involves opening your cervix (neck of the womb) with a small tube known as a dilator, and removing any remaining tissue with a suction device. You should be offered a choice of general anaesthetic or local anaesthetic if both are suitable.

This type of surgery is known as evacuation of retained products of conception (ERPC). You may also hear it referred to as surgical management of miscarriage (SMM).

If your blood group is RhD negative, you should be offered injections of a medication called anti-D immunoglobin after ERPC. This is necessary to prevent rhesus disease. Read more about preventing rhesus disease.