Miscarriage is defined as spontaneous expulsion of fetus before 24 weeks of pregnancy. Repeated pregnancy losses is when miscarriage happens in every pregnancy with no successful pregnancy in between.The causes of these are manifold as below :
1) Genetic defects - These could be in the baby or mother. Many a times chromosomal abnormalities in the fetus result in spontaneous miscarriage. Chromosomal abnormalities in the mother can be inherited in the baby causing an imbalance in the number of chromosomes thereby resulting in a miscarriage.
2) Structural defect - In the uterine structure give less space for the baby to grow and compromise on blood supply thereby resulting in abortion.
3) Environmental exposure - These could be in the form of medicines that are harmful to babies, infections and chemical or radioactive exposure.
4) Metabolic disease in mother - Hormonal imbalances caused by diseases like thyroid disease can cause miscarriage. Also diseases like diabetes or arthritis are known to cause abnormalities in pregnancy.
The cause of miscarriage can be tested for and appropriate treatment can be given alongwith tests during pregnancy to ensure baby does not have chromosomal abnormalities. Treatment given before the lady becomes pregnant (preconception) gives the best results.