Recurrent miscarriage is defined as two or more consecutive miscarriages before the 15 week of pregnancy. Sporadic miscarriages can occur in 10-15% of all pregnancies in the first or second trimester and typically before the 12 week of pregnancy.
The risks of having subsequent miscarriages increases as follows:
- 24% after two miscarriages
- 30% after three miscarriages
- 40% after four consecutive miscarriages
The causes of miscarriages can be divided into six categories:
In approximately 2-4% of couples with recurrent miscarriages, one partner will have a genetically balanced chromosomal abnormality. Balanced translocations account for the majority of chromosomal abnormalities. A blood test of both the husband and wife can detect these abnormalities.
Approximately 60% of miscarriages are due to chromosomal abnormalities in the fetus. The most common cause is an aneuploidy which is an abnormal number of chromosomes. Chromosomes can also be broken or have other abnormalities. A chromosomal analysis from the conceptus is obtained during a dilitation and curettage to rule out abnormalities in the fetus. PGD can often be used to rule out chromosomal abnormalities.
Hormonal and Metabolic Disorders
Luteal phase defect (LPD) - Occurs when the corpus luteum (The site of egg release) fails to produce sufficient progesterone to establish a mature endometrial lining suitable for proper placental attachment. This can be treated by progesterone supplementation post ovulation.
Polycystic Ovarian Syndrome (PCOS) - Studies have shown that as much as 36-56% of women with recurrent miscarriages have PCOS. Women with PCOS who miscarry may have higher levels of androgens and a significant insulin resistance. The risk of miscarriages can be reduced with insulin lowering agents like metformin. Preconception management with lowering of insulin as well as androgens appears to be imperative for reducing miscarriages.
Other Metabolic Abnormalities
Type I insulin-dependent diabetes mellitus
Congenital uterine abnormalities include the bicornuate (uterus with two cavities), septate (uterus with a midline wall) uterus or uterus didelphic (duplication of uterus and cervix). These abnormalities account for 10-15% of miscarriages. This is because the embryo cannot implant and get the nourishment it needs to survive. Most uterine abnormalities can be corrected surgically.
Uterine submucosal fibroids (fibroids in the uterine cavity) as well as scars inside the uterus can also be associated with recurrent miscarriages.
- Listeria Monocytogenes
- Mycoplasma Hominis
- Ureoplasma Urealyticum
- Bacterial vaginosis has been associated with mid trimester pregnancy loss
Most often there are no symptoms, and when diagnosed, these infections can be treated very effectively with antibiotics.
Thrombophilia (hereditary disorders can lead to blood clots)
- Factor V leiden mutation
- Prothrombin mutation
- Protein C deficiency
- Protein S deficiency
- Antithrombin III deficiency
Sometimes immunologic factors may be present which cause the female’s body to mistake the fetus for an invading pathogen. When this happens, her body makes antibodies to the fetus and attempts to destroy it. This antibody reaction causes increased clotting and is responsible for approximately 5% of miscarriages. The physician can perform a blood test to detect some of the immunologic causes of miscarriage:
- Lupus anticoagulant
- Platelet count
- Antiphosphotidylserine IgG and IgM
- Treatment may include a combination of a baby aspirin and Lovanox (blood thinner)