It is highly unlikely that you will ever know the actual cause of a one-off miscarriage, but most are due to the following problems:
• ABNORMAL FETUS
The most common cause of miscarriages in the first couple of months is a one-off abnormal development in the fetus, often due to chromosome anomalies. 'It's not as though the baby is fine one minute and suddenly dies the next,' says Professor James Walker, Professor of Obstetrics and Gynaecology at the University of Leeds.
'These pregnancies fail from the outset and were never destined to succeed.' Most miscarriages like this happen by eight weeks, although bleeding may not start until three or four weeks later, which is worth remembering in subsequent pregnancies. 'If a scan at eight weeks shows a healthy heart beat, you have a 95 per cent chance of a successful pregnancy,' says Professor Walker.
• HORMONAL FACTORS
A hormonal blip could cause a sporadic miscarriage and never be a problem again. However, a small number of women who have long cycles and irregular periods may suffer recurrent miscarriages because the lining of the uterus is too thin, making implantation difficult.
Unfortunately, hormone treatment is not terribly successful.
'There used to be a trend for progesterone treatment, but trials show this really doesn't work,' warns Professor Walker. 'There is some evidence that injections of HCG (human chorionic gonadotrophin, a hormone released in early pregnancy) can help, but it's not the answer for everyone.' The treatment must be started as soon as the pregnancy is confirmed, at around four or five weeks.
For women over 40, one in four women who become pregnant will miscarry. [One in four women of all ages miscarry, but these figures include women who don't know that they are pregnant. Of women who do know that