Recurrent pregnancy loss is defined by two or more failed pregnancies. Depending on how far along the pregnancy was at the time of the loss, the medical background of the male and the female, and other factors, an evaluation will be undertaken. This evaluation will attempt to determine the cause of the losses, and will be used to develop a treatment plan to prevent future losses. In up to half of couples, despite a thorough evaluation, no cause will be found.
Among the various causes of pregnancy loss are the following:
- Genetic/Chromosomal Causes – Translocation (when part of one chromosome is attached to another chromosome) is the most common inherited chromosomal abnormality. Although a parent who carries a translocation is frequently normal, their embryo may receive too much or too little genetic material. When this occurs, a miscarriage usually occurs. Couples with translocations or other specific chromosome defects may benefit from pre-implantation genetic diagnosis (PGD) in conjunction with IVF.
- Age – The chance of a miscarriage increases as a woman ages. After age 40, more than one-third of all pregnancies end in miscarriage. Most of these embryos have an abnormal number of chromosomes.
- Hormonal Abnormalities – Progesterone, a hormone produced by the ovary after ovulation, is necessary for a healthy pregnancy. Low progesterone levels, often called luteal phase deficiency, may cause repeated miscarriages. Treatments may include ovulation induction, progesterone supplementation or injections of human chorionic gonadotropin (hCG).
- Metabolic Abnormalities – Women with diabetes improve pregnancy outcomes if blood sugars are controlled before conception. Women who have insulin resistance, such as obese women and many who have polycystic ovarian syndrome (PCOS), also have higher rates of miscarriage.
Uterine Abnormalities – Distortion of the uterine cavity may be found in approximately 10% to 15% of women with recurrent pregnancy losses. Diagnostic screening tests include hysterosalpingogram, ultrasound, or hysteroscopy. Congenital uterine abnormalities include a double uterus, uterine septum, and a uterus in which only one side has formed. Asherman’s syndrome (scar tissue in the uterine cavity), uterine fibroids, and possibly uterine polyps are acquired abnormalities that may also cause recurrent miscarriages. Some of these conditions may be surgically corrected.
Antiphospholipid Syndrome – Blood tests for anticardiolipin antibodies and lupus anticoagulant may identify women with antiphospholipid syndrome, which causes up to 15% of recurrent miscarriages. In women who have high levels of antiphospholipid antibodies, pregnancy outcomes are improved by the use of aspirin and heparin (a blood thinner).