One in two hundred couples will experience two or more consecutive miscarriages. Below are the main reasons behind miscarriages; some women will have multiple reasons:

• Infections cause about 1% of cases and include bacterial, viral, parasitic, fungal, or those acquired through sexually transmitted diseases.
• Abnormal anatomy causes 4-10% of miscarriages and includes problems such as distortion of the uterine cavity or adhesions from disease or surgery.
• Progesterone level low accounts for 20%.
• Chromosomal abnormalities account for 7% of cases in primary miscarriers (those with no previous live births) and 50% of secondary miscarriers (those with at least one live birth).
• Immune mechanisms / abnormal antibodies cause 50% of miscarriages.
• Endocrine or hormone disorders such as diabetes (when poorly controlled) and hyper- or hypothyroidism.
• Other factors of conception such as defective sperm cells, time of egg implantation, or stress.
• Unknown factors are the cause of about 15%.

Who is Most At Risk?
People with the following conditions or characteristics are at risk of having a miscarriage:

• Previous spontaneous abortion
• Women age 35 or older
• Cigarette smoking - smoking half a pack or more per day significantly increases risk
• Alcohol risk doubles with more than two drinks per day
• Caffeine consumption
• Cocaine use
• X-ray exposure and long periods spent in airplanes e.g. flight attendants
• Environmental toxins - excessive exposure to lead, mercury, organic solvents
• Serious maternal illness
• Maternal or paternal handling of anti-cancer agents
• Increased levels of homocysteine

Treatment
Various dietary and lifestyle factors play a part in causing miscarriages and recommendations can be found below.

Eating fish contaminated with pollutants, namely persistent organochlorine compounds (POCs), may increase pregnancy risks, although it is not clear whether eating contaminated fish contributes to spontaneous abortion.

Prognosis and Possible Complications
There is only about a 1% chance of recurring miscarriage; however, the risk increases significantly with each subsequent loss. Possible complications from spontaneous abortion include infected pregnancy tissue, which could lead to pelvic abscess, septic shock, or even death. Depression and guilt are common feelings that may follow a miscarriage; there are times when counseling is appropriate.

Dealing with Immune Mechanism Problems
Advances in immunology have enabled an understanding of how, during pregnancy, the mother's immune system is altered so that the fetus is not rejected by her body and allows the fetus to grow. When the immune system is the cause of miscarriage, the chances of the mother having a successful pregnancy without treatment after 3 miscarriages is 30%, after 4 miscarriages 25%, and after 5 miscarriages 5%.

• BLOCKING ANTIBODIES
  Early in pregnancy, the mother's immune system receives signals from the tiny fetus. Many of the signals are hormonal, but others come directly from genetic messages that the father has contributed. Some of the messages involve the tissue type, also known as the human leukocyte antigens (HLA) and the white blood cell (leukocyte) type.
  
  If there is a problem here, treatment involves immunizing the mother with concentrates of the father's white blood cells so that the HLA (human leukocyte antigen) signals are amplified. When blocking levels are elevated prior to conception, the rate of successful term pregnancy is approximately 80%.


• ANTIPHOSPHOLIPID ANTIBODIES
  Phospholipid molecules are normal components of all cell membranes and antibodies to phospholipid molecules can therefore interfere with the development of the placenta. With each pregnancy loss, there is a 10% chance that the mother will develop an antibody to a phospholipid molecule. Most women with antiphospholipid antibodies are not sick. However, some have underlying autoimmune tendencies and should be appropriately evaluated. Women with underlying autoimmune diseases may have antiphospholipid antibodies even before they ever become pregnant.
  
  The treatment for antiphospholipid antibodies involves the use of low dose (baby) aspirin and an animal-derived blood thinner called Heparin. The effectiveness of treatment is much greater when the medication, if indicated, is started prior to conception and continued throughout the pregnancy. All medication should be discussed with one's physician.


• ANTINUCLEAR ANTIBODIES
  The nucleus is the " brain " of the cell. It contains the information that regulates the function of the cell. Some people have antibodies to different nuclear components. The disease that we typically associate with antinuclear antibodies is Systemic Lupus Erythematosus (SLE). The miscarriage rate in SLE patients is much higher than that of the general population. Although most women who suffer recurrent miscarriages do not have clinical signs of SLE, many exhibit autoimmune phenomena that are similar to those seen in SLE patients. The placentas in these women are inflamed and weakened.
  
  The treatment for this problem is Prednisone, a corticosteroid, which suppresses the inflammatory process and stabilizes the cell. Prednisone does not pass through the placenta easily and is also broken down by enzymes in the placenta so that the fetus is exposed to only trace amounts. Additionally, the body produces the equivalent of 8mg per day of this corticosteroid. When indicated, Prednisone should be started prior to conception.


• IMMUNOPHENOTYPES: NATURAL KILLER CELLS AND CYTOTOXIC B-CELLS
  The immune system is composed of more than 30 types of white blood cells including neutrophils, monocytes and lymphocytes. Lymphocytes, particularly B-cells (antibody producers), T-cells (helper and suppressor) and killer (NK) cells have been the focus of intense research interest to the discipline of reproductive immunology. Immunophenotype refers to the relative amounts of T, B and NK cells in the bloodstream.
  
  Women who have an elevation of NK cells are candidates for immunologlobulin G infusion (IVIg). A recent study reports an 80% success rate in women who either had a history of miscarriage despite optimal immunotherapy (paternal leukocyte immunization, aspirin, heparin and prednisone), or had a history of IUGR.


• INHERITED THROMBOPHILIAS
  The Inherited Thrombophilias comprise a group of genetic disorders of the blood clotting pathways, leading to abnormal blood clot formation. Women who carry the genes for Inherited Thrombophilias are more likely (2 to 14 times) to have a clotting problem leading to a miscarriage, compared with the normal population.
  
  Homocysteine is normally present in low levels in the bloodstream. A gene mutation in the enzyme methylene-tetrahydrofolate reductase (MTHFR) will lead to build up of homocysteine in the bloodstream, called hyperhomocysteinemia, and this results in blood clot formation and hardening of the arteries. Nutritional lack of vitamins B6, B12 and folic acid aggravate the problem. Women who have the homozygous form of the MTHFR gene mutation (both alleles having the mutation) have more than twice the risk of a miscarriage.
  
  Treatment usually involves a combination of low-dose aspirin plus low molecular weight heparin injections. The therapy is started before pregnancy occurs, and continued four to six weeks after birth. Folic acid supplementation is given to patients with the MTHFR gene mutation.