A miscarriage is the loss of a pregnancy before 22 - 24 weeks of pregnancy. It happens to about 15 per cent of women who are expecting and is more common than most people know.

More than 80 per cent of miscarriages occur in the first trimester of pregnancy. Although it is less likely for a woman to lose her foetus after the first 12 weeks, or first trimester, they can still occur. These are termed late miscarriages.

Some scientists believe that chromosome abnormalities is the main reason for early miscarriages. Perhaps through natural selection, a woman's womb will reject a foetus when there is something seriously wrong with the foetus our body. But this is hard to explain because our genetic setup is so complex and precise. This reason alone may account for more than 50 per cent of all early miscarriages.

Other causes of miscarriages that are less common include:

1) Infection. Serious infections include listeriosis (gotten through consuming contaminated dairy products, uncooked food), toxoplasmosis (transmitted through cats' faeces) and rubella;

2) Chronic illness in the mother. Conditions such as diabetes, thyroid problems, hypertension and renal disease, especially when these conditions are left untreated;

3) Autoimmune conditions such as systemic lupus, anti-phospholipid syndrome (triad of recurrent miscarriages,
tendency for blood clot formation, presence of antiphospholipid antibodies);

4) Uterine abnormalities, - such as an abnormally shaped uterus that may not be able to "hold" or support a pregnancy;

5) Substance abuse such as alcohol consumption, taking drugs and smoking. Toxins in the bloodstream are harmful to the developing foetus.

6) Age of the mother. The risk of miscarriage increases as the mother's age increases. An increase in her age is directly related to a drop in the quality of the eggs she produces.

Got a question on your reproductive health? Email it to us at Just Woman and we will get it answered by Dr Fong Yoke Fai, a consultant Obstetrician and Gynaecologist at the National University Hospital.