• Genetic / Chromosomal Problems
• Uterine abnormalities
• Hormonal Imbalance
• Immunity disorders
• Diseases in mother
• Environmental & Lifestyle factors.

Genetic Causes
The major cause (50 – 60%) of early miscarriage is probably a genetic factor. The most common genetic defect resulting in miscarriage is an abnormal number or structure of chromosomes. Often this is a nature’s way of ending a pregnancy in which the fetus was not rowing normally and would not have been able to live. The numerical abnormalities are usually non-repetitive (do not have an increased risk of recurrence in subsequent pregnancies). The structural chromosomal abnormalities are usually inherited from a parent with a balanced translocation or inversion, and are repetitive.

In order to determine whether there is a genetic cause, your doctor may order a karyotype on the fetal tissue (obtained during a D&C) and on blood from both parents. If the karyotype is abnormal, there is no therapy available, but the information help explain the cause in these patients. In about 5% of patients with recurrent miscarriage, a balanced translocation or inversion is found in one of the parents. If both parents have a normal karyotype, it is likely that the miscarriage was a chance event, and they should feel comfortable to plan a next pregnancy. In cases of abnormal karyotype, genetic counseling to discuss the degree of risk may be recommended.

Uterine Abnormalities
Approximately 10 – 15% of women with a history of recurrent miscarriage have an abnormally shaped uterus. The commonest example is a septate uterus, which involves a central ridge or partition protruding into the uterine cavity (Fig 1). Septate uterus occurs in about 3% of women and about half of these have reproductive difficulties. Other birth defects in uterine shape (congenital uterine malformations) can likewise result in pregnancy loss.

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One subset of women with uterine abnormalities is those whose mothers took diethystilbesterol (DES) while pregnant. DES women have a significantly higher incidence of miscarriage, premature labor and infertility.

Uterine fibroids, especially those which grow in the cavity (submucous fibroids) can distort the shape of the uterine cavity can interfere with the implantation or growth of the fetus. Fibroids can increase in size during pregnancy and cause miscarriage.

These abnormalities can be easily diagnosed using high resolution ultrasonography, a special x-ray called hysterosalpingography (HSG), or by direct examination of the uterine cavity using hysteroscopy (an endoscopic examination of the uterine cavity).

The cervix can be congenitally weak or become weak due to previous miscarriages or surgical trauma, unable to support the pregnancy. About 20% of mid-trimester (16 -20 weeks) pregnancy losses are caused by this condition, called cervical incompetence. Once diagnosed, the subsequent pregnancy can be carried to term by a surgical procedure called cerclage or cervical stitch.

Hormone Imbalance
The luteal phase or the second half of the menstrual cycle, is a critical time when the endometrium (lining of the uterus) responds to the hormone progesterone, which is produced by the ovary after ovulation. If the progesterone production is low, infertility or miscarriage can result. This occurs because the endometrium fails to become a nourishing environment, preventing the embryo from implanting securely. This problem is called the luteal phase defect, which can result from abnormal hormone levels or poor ovulation, and is easily corrected by hormones (progesterone) or by correcting ovulation using ovulation induction drugs.

Immunity Disorders
The immune system plays an important role in maintaining health and responding to infection, injury or introduction of foreign material. At this time, the immunologic interaction between the mother and fetus is no clearly understood, but it falls in two general categories.

The first category involves the production of certain immunoglobulins or antibodies which the pregnant women’s body creates and directs against circulating substances that affect blood clotting. Examples of these antibodies are lupus anticoagulant, anticardiolipids, and the antiphosholipids. These antibodies affect fetal development, often resulting in recurrent miscarriage. Therapy includes aspirin, heparin or steroids in small doses. Although these mediations may pose health risks, in selected cases, the pregnancy outcome can be dramatically improved.

The second category involves an alteration in the immunologic response of the mother against the pregnancy. During a normal pregnancy, the fetus, which carries the father’s foreign genes, survives in the mother’s uterus because of a special protective response from the mother’s immune system. In couples with recurrent miscarriage, this protective response does not occur, and the maternal immune system is activated to reject the (foreign) fetus. Immunization (paternal leucocyte transfusion) to prevent the maternal immune system from ejecting the fetus is available.

Maternal Illness
Certain maternal diseases have been associated with a higher rate of pregnancy loss. These conditions include autoimmune diseases, thyroid disease, severe uncontrolled diabetes, sere kidney disease and congenital heart disease. Treatment of some of these diseases before conception can improve chances for successful pregnancy.

Environmental and lifestyle Factors
Smoking, drinking, and abuse drug use can increase the risk of miscarriage. However exercise, working, intercourse, travel and exposure to computer terminals do not increase the risk of miscarriage. If couples are concerned that their home or work environment may be hazardous, they should consult their physician about this issue. Although most medicines do not have an effect on pregnancy, there are some which may be harmful and lead to miscarriage and birth defects. Women should always consult their physician before taking any medicines during pregnancy, and also need to alert doctors or dentists before receiving x-rays or prescriptions for medication.

DIAGNOSTIC TESTS
As recurrent miscarriage can be due to many possible causes, your doctor will require a detailed history, clinical examination, laboratory tests, x-rays, diagnostic endoscopy to come to a working diagnosis.

These tests include:

Your doctor will decide which tests to order, depending on the individual case. The treatment will depend on the cause found.

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