Most cases of habitual abortion result from an inadequate secretion of the female hormone progesterone. This hormone is responsible for the development of the placenta. In the early stage of pregnancy, the gonadotrophin secreted by the cytotrophoblast of the chorine, one of the fetal membranes, stimulates the corpus lotemum to produce more estrogen and progesterone, both essential female hormones. At a later stage, by about the 12th week of pregnancy, the placenta takes over the production and secretion of the hormones. Any deficiency of these hormones at this stage is detrimental to the growth of the fetus. It is, during this critical period, when habitual abortion mostly occurs. Lack of progesterone is especially instrumental in expelling the fertilized ovum and it results in an abortion.
Another important cause of habitual abortion may be chronic constipation which leads to putrefaction of morbid matter and wastes in the large intestines. This, in turn, causes auto-intoxication and inflammation of the reproductive organs, which can lead to a miscarriage.
Abortion may result from the excessive use of certain drugs. Drugs enter the fetus through the placenta. They may act quite differently on the fetus from the mother. Drugs which have adverse effects on the fetus are called "tera-togenestic drugs" and may include painkillers, antibiotics, tranquilizers, and hormones. A high dosage of such drugs may produce contraction in the uterus and induce abortion.
Other causes of habitual abortion are excessive physical exercise, mental excitement, sexual intercourse, syphilis infections fibroid tumors, blood incompatibly of husband and wife, systemic disorders in the mother like hypertension, chronic nephritis, diabetes and even her mental condition.
A thorough examination of the pregnant woman’s blood, urine, blood pressure and their related parameters help in detecting maternal disorders. Serological tests prove the presence or absence of syphilis infection. Pelvic examinations help to diagnose uterine displacements, fibroids or ovarian tumors. A hysterogram also helps to detect uterine malfunctions. The exact cause must be ascertained for prescribing the correct treatment.