AMERICAN specialist Dr Jonathan Scher de-mystifies miscarriage in his book Preventing Miscarriage: The Good News (Harper and Row), in which he presents findings on the causes and prevention of recurrent miscarriage: Chromosomal errors are the most common cause of miscarriage in the first 12 weeks. While this is thought to be a chance event, if further miscarriages occur it is possible that a couple has a chromosome defect within their cells that they are passing on to their child. Dead foetal tissue can be tested for this. Doctors cannot yet cure genetic defects.
Some pregnant women may have a blood clotting disorder. When clots form in the placenta, vital nutrients cannot reach the foetus. The condition can be treated with anti-clotting agents or with cortisone-like drugs.
Infections, ranging from sexually-transmitted diseases such as chlamydia and syphilis to German measles may cause miscarriage. Once the infection has been identified it may be treated.
Some women do not produce enough progesterone, considered the most important hormone in early pregnancy. Many specialists prescribe progesterone to maintain the pregnancy in the early weeks.
Defects in the uterus may make it hard to carry babies to term. Among the most common is the ''incompetent cervix'', which can cause miscarriage after 14 weeks. This can be remedied by a stitch around the cervix to tighten it. A misshapen uterus, another cause, can also be treated surgically.
Medical disorders including thyroid and kidney diseases, uncontrolled diabetes and lupus are all associated with miscarriage.
No one knows for certain if various substances and radiation levels can cause miscarriage. Products under suspicion range from video display terminals and copying machines to household bleaches and microwave ovens.
COPING can be contacted through the Community Advice Bureau