A miscarriage is the loss of a pregnancy in the first 23 weeks.
Miscarriage is common. It is possible that as many as 50% of pregnancies ‘miscarry’ before implantation in the womb occurs, so you do not realise you are pregnant.
Most miscarriages occur in the first 12 weeks of pregnancy. Overall about 1 in 6 of all pregnancies (15%) end in miscarriage. The risk of miscarriage decreases as pregnancy progresses. Early after implantation, pregnancy loss rate is about 3 in 10 (30%). Again this is still before a pregnancy is clinically recognised.
After a pregnancy may be clinically recognised with a pregnancy test (between days 35-50), about 1 in 4 (25%) will end in miscarriage.
Recurrent miscarriage is the loss of three or more consecutive pregnancies. Around 1 in 100 women (1%) have recurrent miscarriages. This is 3 times more than would be expected by chance (calculated risk should be about 1: 300 women or 0.3%).
So for about 2/3 of women with recurrent miscarriage there must be a specific reason for their losses. However we may not always be able to find out what the cause is, or treat it.
There are a lot of theories and treatments for recurrent miscarriage but few have been shown to be scientifically sound.
The development of specific Miscarriage Clinics with appropriate expertise have been suggested in a recent publication of the British Journal of Obstetricians and Gynaecologists (Feb 1996 pages 106-110) though this service has been available in Sheffield for some time.
We offer a Pre-Pregnancy Counselling Service where you (and your partner) will be offered a sympathetic consultation with an experienced Consultant with expertise in the investigation and treatment of women with recurrent miscarriage.
The relevant investigations and treatment will be discussed and a management plan formulated for your subsequent pregnancy wherever you choose to deliver.
A number of factors play a role in recurrent miscarriage. The problem is complex and further research is needed.
Age and past pregnancies
Older women are more likely to have miscarriages. The more miscarriages that a woman has had, the more likely they are to have another.
Endocrine or Hormonal causes
Polycystic ovaries may be related to recurrent miscarriage. This is not a direct cause – the link is unclear.
Elevated luteinising hormone (LH) found in Polycystic Ovarian Syndrome may play a part in recurrent miscarriage. This can be treated if the diagnosis is confirmed on a pelvic ultrasound scan.
Although traditionally blamed in the past, well controlled diabetes and thyroid disease do not appear to be a cause.
Hyperprolactinaemia. Prolactin prepares the pregnant woman’s breasts to produce milk. The evidence relating to excessive prolactin production and recurrent miscarriage is conflicting.
Genetic or chromosomal causes
Chromosome abnormalities may be present in either the woman or her partner. These abnormalities may have no obvious effect on the carrier, but may cause about 3-5% of cases of recurrent miscarriage. This can be excluded by both partners having a simple blood test. If either test is abnormal then referral to a Clinical Geneticist will be arranged for counselling.
Abnormalities in the embryo
This is the most common reason for single miscarriages. It is less likely to be the cause of recurrent miscarriage.
Immune system and Blood Clotting
Antibodies are normally produced to fight infections. When these antibodies act against the body this is know as an autoimmune response.
Antiphosphospholipid antibodies (aPL) are seen in around 155 of women with recurrent miscarriage. They may also cause blood clots (eg in the leg known as a DVT) or a low platelet count (a deficiency of small cells in the blood responsible for clotting and hence a tendency to bruising).
Certain inherited conditions lead to an increase in the likliehood of blood to clot. These conditions are known as thrombophilias. The link between thrombophilia and recurrent miscarriage is unclear.
These conditions can be investigated by blood tests. Up to 15% of women with recurrent miscarriage have aPL syndrome though it is found in about 2% of normal women. aPL in women with a normal past obstetric history causes a pregnancy loss rate of 50-75%. If they have had recurrent miscarriages and are not treated the loss rate rises to 90%. The exact mechanism is not understood but aPL seems to affect the placenta (afterbirth) and its supply of blood and nutrients to the baby.
Various treatments are available, depending on the problem, including low dose aspirin (75mg daily), heparin (Clexane) injections and steroids (Prednisone) with successful pregnancies in up to 80% treated cases. Clexane is given as a self administered subcutaneous injection (20mg daily) and unlike older heparin preparations does not cause significant osteoporosis (loss of calcium from the bone). It can however reduce the platelet count (small blood cells responsible for clotting) and this will be checked after 7-10 days of treatment.
Severe persistent infection usually making the woman unwell and often associated with a fever and rash is a recognised cause in some women. The organisms involved include Rubella (German Measles), Toxoplasmosis and Listeria.
Bacterial Vaginosis, an upset in the normal vaginal organisms found in all women can cause mid pregnancy losses and premature labour but not early miscarriage. A vaginal swab and blood test are required to exclude infection.
Abnormalities of the uterus (womb) or cervix (neck of the womb)
The role of abnormalities is not completely understood and is debated. Thes can be related to 2-37% of recurrent miscarriage, depending on the study that is reviewed.
Ultrasound and x-ray investigations can be used to assess abnormalities of the uterus.
Cervical Incompetence – Mid pregnancy miscarriage may be due to an inadequate (‘weak’) cervix. There is no reliable test for the cervix outside pregnancy. Ultrasound during pregnancy may indicate the risk of miscarriage. Occasionally a stitch may be put in the cervix to decrease the risk of miscarriage. This lowers the chance of giving birth early, but has not been proven to improve the chances of the baby surviving. This option will be carefully considered before it is used.
Women who have been properly investigated for recurrent miscarriages in a specialised centre and who have been found to have no underlying risk factors for their miscarriages can be reassured that they have an 80% chance of a livebirth in a subsequent pregnancy. They can be offered psychological support and regular ultrasound scans for reassurance during the early weeks of any subsequent pregnancy.
The information above is based on the Royal College of Obstetricians and Gynaecologists ‘Green Top’ guideline. The publication lists the full list of evidence sources used.
There is some evidence that women who smoke are at increased risk of miscarriage and that this risk is related to the number of cigarettes smoked.
Similarly, women with an excessive alcohol intake are thought to be more prone to have a higher rate of miscarriage.
Recent research shows that there is no association between the use of video display units (VDUs) and miscarriage.
Tom provided all the care we needed following a miscarriage. He was able to ensure my subsequent pregnancy was well looked after. I have a beautiful baby boy, who looks just like his 4D scan picture.Sarah (Sheffield)