Approximately one pregnancy in four ends in miscarriage, and most of these occur during the first 12 weeks of pregnancy. For many women, the first indication of miscarriage is vaginal bleeding or discharge, sometimes accompanied by abdominal pain or backache, rather like period pains.

Some women may notice that pregnancy symptoms, such as nausea or breast tenderness disappear. Vaginal bleeding in early pregnancy is called 'threatened miscarriage', but does not necessarily develop into a miscarriage. Many women will go on to have a normal pregnancy.

Ectopic pregnancy

Ectopic pregnancy occurs when the fertilised egg (ovum) becomes implanted at a site in the body other than in the womb lining. An ectopic pregnancy is a potentially fatal condition because it can cause severe internal bleeding. Early diagnosis and surgical treatment are therefore essential.

Symptoms of an ectopic pregnancy include a pain in your shoulder tip, vaginal bleeding (the blood will be more watery than your normal period, sometimes described as looking like prune juice), one-sided abdominal pain and pain when passing stools (faeces) or urine.

Pre-eclampsia

Pre-eclampsia is a condition that only occurs during pregnancy, or immediately after the delivery of the baby. Women develop high blood pressure (hypertension) together with protein in the urine and fluid retention (oedema). Symptoms include sudden swelling of your face, hands, feet and ankles, rapid weight gain, vision problems (blurring or flashing lights in front of your eyes), abdominal pain and headaches.

Pre-eclampsia develops in about one in 10 pregnancies, usually after the sixth month of pregnancy. Most cases are mild, develop towards the end of the pregnancy, and are easily treated. However, in a severe form it can be life-threatening for both mother and baby.

Placenta praevia

Placenta praevia occurs when the placenta covers part or all of the cervix (the baby's exit from the womb). It may cause bleeding in the pregnancy and, if the placenta does not move up as the pregnancy progresses, a caesarean birth will be necessary. In most women, the placenta moves out of the way before birth, but additional ultrasound scans may be required to monitor the situation.

Where an earlier placenta praevia has moved out of the way before birth, the risk of a vasa praevia must be eliminated. A vasa praevia occurs when one or more of the baby's placental or umbilical blood vessels cross the entrance to the cervix beneath the baby, and can be ruptured or compressed with the onset of labour. If this is diagnosed, a caesarean birth will be necessary.

Down's syndrome

Other tests during pregnancy can detect any chromosomal conditions, such as Down's syndrome. This occurs when one of the 23 pairs of chromosomes (inherited from each parent) has an extra chromosome attached, resulting in learning disabilities and sometimes health problems. Women at higher risk of carrying a baby with such conditions may opt for testing procedures like amniocentesis or chorionic villus sampling (CVS).

Obstetric cholestasis

Obstetric cholestasis is a rare complication that occurs during pregnancy and is caused by a build-up of bile (a naturally occurring chemical) in your bloodstream. The exact cause of obstetric cholestasis is not yet known, although some researchers suggest that it may be a result of a reaction to the hormone changes that occur in your body during pregnancy. The condition may also run in families.

Obstetric cholestasis is a rare condition that affects approximately 0.1-1.5% of pregnancies. However, it can cause serious complications, significantly increasing the risk of your baby being born prematurely.

Some babies also experience foetal distress. This is when your baby shows signs of being in trouble, such as a change in their heart rate, or their movement. In severe cases, a small number of babies (approximately 2%) are stillborn.

The main symptom of obstetric cholestasis is intensely itchy skin. The itching is normally worst on your:

The itching also tends to be worse at night. Other symptoms of obstetric cholestatis include:

• difficulty sleeping,
• lethargy,
• lack of appetite,
• nausea, and
• jaundice (yellowing of the skin).

An estimated one in 5 women experience some itching during their pregnancy. However, for most women, it is a result of the stretching of their skin, as well as an increased blood supply to the skin. If your itching becomes particularly intense, or it is accompanied by any of the other symptoms above, you should contact your GP or midwife for advice.

If you are diagnosed with obstetric cholestasis, you and your baby will be carefully monitored. Medication can help to control the itching, and you may require an induced labour, or caseseran birth, to help ensure that your baby is not affected by the build-up of bile.

Molar pregnancy

Another rare complication is molar pregnancy. For every 500 babies born in England and Wales, there is around one molar pregnancy (0.2%).

In a molar pregnancy, when the sperm fertilises the egg, the fertilised cell cannot develop into an embryo, due to genetic abnormalities. However, the layer of cells (trophoblast cells) that would eventually become the placenta continues to develop. Sometimes called a hydatidiform mole, this growth of cells continues to produce the pregnancy hormone, hCG (human chorionic gonadotrophin), at an abnormally high level.

Most molar pregnancies are diagnosed quite early, perhaps as a result of bleeding, or following an ultrasound scan. If left untreated, molar pregnancies normally result in miscarriage.

If you have a hydatidiform mole, it can usually be treated in a small operation, which is carried out under general anaesthetic. After treatment, your level of hCG will probably be monitored. In most people, the level will fall. However, if it stays the same, or continues to rise, further treatment may be needed.

After a molar pregnancy, you may be advised to wait for 12 months before trying for another baby.

Stillbirth

If a baby is born after 24 weeks of pregnancy, and does not show any signs of life at any time after being born, it is known as a stillborn baby. Sometimes, the cause of death is clear. However, in many cases the cause of death cannot be established.

The stillbirth rate in the UK is 5.5 per 1,000 births (about 0.5%). There is a slightly higher risk for women under the age of 20 - 6.6 per 1,000 - (about 0.6%), and women aged over 40 - 7.2 per 1,000 - (about 0.7%).

Not smoking during pregnancy will reduce the risk of a stillbirth.

Many stillbirths are preceded by a reduction in the baby's movement. If you feel that your baby has 'gone quiet', contact your midwife or GP immediately.

A stillbirth can be a traumatic experience for parents. Many find that bereavement counselling helps them come to terms with their loss.

A stillborn baby must be cremated or buried. Many couples have found that holding a proper funeral for their baby helps in coping with the trauma of losing their child.