Uterine abnormalities. This may include presence of fibroids in the uterine cavity, very large fibroids in the wall of the uterus, presence of a uterine septum, and other conditions such as a unicornuate uterus (half a uterus) or a double uterus.
- Cervical abnormalities. This is a rare cause. Women who have this cause most commonly have a weak cervix due to prior surgeries to the cervix to treat early cervical cancer.
- Genetic abnormalities of the baby. If the baby begins development with an incorrect balance of genes, it can lead to poor development of the baby and loss of the pregnancy.
- Genetic abnormalities of the mother or father. Prospective parents can carry genetic abnormalities themselves and not know it. When their chromosomes combine to make a baby, the baby does not develop normally and miscarries. This can be determined through examination of the chromosomes of the couple.
- Advancing age of the female. As women age, their ovaries age and thus their eggs age. If an egg becomes too old but still gets fertilized by a sperm, it can lead to abnormal development of the early pregnancy and therefore be at a higher risk of miscarriage.
- Polycystic ovarian disease. Some women with this condition (irregular periods, pre-diabetes, infertility, abnormal growth of body hair in a male pattern) are believed to be at increased risk of miscarriage. Some research studies have suggested that 36-56% women with recurrent miscarriage have PCOS.
- Metabolic disorders. Women with poorly controlled diabetes (insulin-dependent) have an increased rate of miscarriage. However, there is no evidence to suggest that asymptomatic women with mild thyroid disease have a higher miscarriage rate.
- Problems with clotting factors in the blood. Some women may have acquired or inherited problems with components of the blood clotting process. These problems can increase the woman’s risk of having a blood clot and are thought to also increase a woman’s chance of having microscopic blood clots in the blood vessels to the uterus or to the lining of the uterus when pregnant. This in turn can increase the risk of early miscarriage.
- Autoimmune disorders. Some women can have a condition known as antiphospholipid syndrome. This is an autoimmune disorder characterized by the presence of significant levels of antiphospholipid antibodies in the blood which may put the woman at increased risk of recurrent miscarriage and blood clots. Women may be born with this condition or acquire it during their life.
The majority of women do not have an identifiable cause of recurrent miscarriage. This does not mean that nothing can be done or that they are destined to have another miscarriage. Studies show that even with 5 or more consecutive miscarriages, the next pregnancy has a 50% chance of going to full-term with no treatment at all. Other studies show that frequent visits to the physician with ultrasounds to check on the developing pregnancy help to reduce the risk of miscarriage.