What causes a miscarriage?

A miscarriage is a pregnancy that ends before 24 weeks, which is before most developing babies are able to survive outside the womb (uterus).

About miscarriage

Miscarriage is very common and occurs in about one in five pregnancies. Most happen in the first 12 weeks of pregnancy.

Recurrent miscarriages are when you lose three or more pregnancies in a row. This is uncommon and affects only one in every 100 couples.

If you have a miscarriage, even recurrent miscarriages, it's unlikely that you have an underlying medical problem, and most women go on to have a successful pregnancy in the future.

Types of miscarriage

There are different types of miscarriage as described below.

Threatened miscarriage: This is when you have bleeding early in your pregnancy and your cervix (the opening to your womb) is tightly closed. Your pregnancy is likely to continue if an ultrasound scan shows the heartbeat of your developing baby.

Inevitable miscarriage: This is when you have bleeding early in your pregnancy and your cervix is open, which means your pregnancy will be lost.

Incomplete miscarriage: This is when a miscarriage has started but there is still some tissue left in your womb. Your cervix is usually open.

Complete miscarriage: This means that your pregnancy has been lost. Your womb is empty and your cervix has closed.

Delayed or missed miscarriage: This means that although your developing baby has died, you haven’t had any bleeding and didn’t lose any tissue straight away.

Symptoms of miscarriage

The most common symptom of a miscarriage is bleeding from your vagina. This can vary from light spotting to bleeding that is heavier than your period.

You may see blood clots or a brown discharge. You can also have cramps and pain in your abdomen (tummy), pelvis or back.

If you have bleeding from your vagina at any time during pregnancy, you should contact a doctor, midwife or obstetrician immediately for advice.

Some people don’t have any symptoms and their miscarriage may only be discovered in a routine scan.

Causes of miscarriage

About half of all early miscarriages happen because of a problem in the way your genetic material (chromosomes) combined when your egg and your partner's sperm joined during fertilisation.

You may never find out why this has happened, but it's more likely to be due to chance than to any underlying problem with either you or your partner.

Other factors that can make a miscarriage more likely include:

• problems with your immune system
• having an infection, such as listeria or malaria
• your age – half of all pregnancies in women over the age of 42 end in miscarriage
• a physical problem with your reproductive system
• health problems, such as poorly controlled diabetes, a kidney disease or polycystic ovarian syndrome
• drinking alcohol while you're pregnant
• smoking while you’re pregnant

There isn't any evidence to show that stress is a risk factor for miscarriage, but it's a good idea to take time during the day to relax.

Moderate exercise or having sex while you're pregnant doesn't increase your risk of miscarriage.

Often you won't know what has caused your miscarriage. If you have already started to miscarry there is nothing that can be done to prevent it.

Diagnosis of miscarriage

A doctor will ask about your symptoms and examine you. He or she may also ask you about your medical history.

The doctor may refer you to a gynaecologist (a doctor who specialises in women's reproductive health), or to a hospital to have further tests, including those listed below.

• An ultrasound scan - this uses sound waves to produce an image of the inside of your womb.
• Blood and urine tests can measure hormones associated with pregnancy called beta-human chorionic gonadotrophin and progesterone.
• An examination of your pelvis to check the source of any bleeding.

Recurrent miscarriages

If you have recurrent miscarriages, the doctor may refer you and your partner to a gynaecologist to have some tests to rule out a specific cause.

Possible causes include a hormonal disturbance, inherited problems, abnormalities of your womb, or a condition where your body's own defence mechanism attacks itself, leading to blood clots forming in the placenta.

Please note that availability and use of specific tests may vary from country to country.

Treatment of miscarriage

If your miscarriage is complete, you won't usually need any further treatment. For an incomplete or missed miscarriage, or when you have a lot of bleeding, you may need treatment with medicines or surgery to remove the remaining foetal tissue.

However, some women may prefer to let nature take its course (this is called expectant management).

Your chances of having a healthy pregnancy in the future are just as good whichever method you choose.

Expectant management

This allows the pregnancy to leave your body naturally. It can take some time before any bleeding starts and it’s normal for this to continue for up to three weeks, along with tummy cramps.

You may need to take medicines or have surgery if this method isn’t successful.

Medicines

Medicines will open your cervix and allow foetal tissue to pass out. You may be advised to swallow tablets or a pessary can be inserted directly into your vagina.

The effects of the tablets usually begin within a few hours. You will experience symptoms similar to a heavy period, such as cramps and vaginal bleeding.

The bleeding can continue for several weeks, although it won’t be heavy for very long.

Always ask your doctor for advice and read the patient information leaflet that comes with your medicine.

You may need to have surgery if medicines are unsuccessful.

Surgery

Whether or not you need surgery to remove any tissue will depend on the stage of your pregnancy, the amount of bleeding you're having, and your own preferences.

Surgery for miscarriage is a short procedure to empty your womb. It's known as an evacuation of retained products of conception (ERPC).

Your surgeon will pass a soft plastic tube through your cervix into your womb and the remaining tissue will be removed by suction.

The operation is usually done as a day case under general anaesthesia. This means you will be asleep during the operation.

Alternatively, you may be given the option of local anaesthesia. This blocks pain from the area and you will stay awake during the operation.

ERPC is commonly performed and generally safe. However, in order to make an informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications. These include:

• excessive bleeding
• a perforation or small hole made in your womb during the procedure (which may require surgery to repair it)

Ask your surgeon to explain these risks to you.

Late miscarriages

If you have a miscarriage between 14 and 24 weeks, you will probably have to go through labour and delivery. The miscarriage may be spontaneous, or labour may need to be induced.

You will have some bleeding and possibly period-like pain in the days after the delivery and for several weeks. Your breasts may produce milk.

It may be possible to have a post-mortem on your baby, which may provide information about what caused the miscarriage and possibly help your doctor to care for you if you have a future pregnancy.

Availability and use of different treatments may vary from country to country. Ask your doctor for advice on your treatment options.

After a miscarriage

The physical effects of a miscarriage tend to clear up quickly. Your next period is likely to follow between four and eight weeks later but it may take several cycles to re-establish a regular pattern.

You may feel physically ready to return to normal activities (such as exercising and going back to work) around a week after an operation, or a few days after treatment with medicines or expectant management.

However, the emotional impact of having a miscarriage can be much greater than the physical effects. A miscarriage can cause a range of feelings.

Everyone reacts differently and there is no right or wrong way to feel. It can be equally difficult for your partner and it’s important to get the support you both need.

You could consider contacting support groups where you can talk with people who may have similar experiences to you.

You may decide to begin trying for another baby right away or you may think this is too soon and you need longer to recover emotionally. There is no right or wrong thing to do, you need to do what you feel is best for you and your partner.

You may be advised by your doctor to wait until you have had at least one period before trying again, although it's safe to have sex when the bleeding and any other symptoms have completely settled and you both feel ready.