Recurrent miscarriage is defined as two or more consecutive, spontaneous pregnancy losses.
Approximately 15% of pregnancies end in miscarriage, which is defined as the loss of a pregnancy before 20 weeks of gestation. Most miscarriages occur within the first 12 weeks of gestation. “Recurrent miscarriage,” also known as “habitual pregnancy loss,” is commonly defined as three or more miscarriages. When miscarriage occurs this frequently, there may be an underlying cause such as a genetic defect. Other causes include an abnormally shaped uterus, uterine fibroids, and scar tissue in the uterus that may hinder implantation or growth of the fetus. Hormonal imbalances of prolactin, thyroid hormone or progesterone can result in miscarriage. Illnesses such as diabetes mellitus or immune system abnormalities may increase the chance of miscarriage.
Treatment for recurrent pregnancy loss can involve a range of options including careful monitoring and pre-natal care, surgery, hormone therapy, antibiotics and the use of procedures such as in vitro fertilization. Appropriate treatment has proved to be both safe and effective for most couples.
Your medical history, a pelvic exam, and one or more of the tests listed below are necessary in diagnosing possible causes of your recurring miscarriages:
Miscarriages appear to be a natural process to protect a woman from a pregnancy that is abnormal. Most losses are due to a chromosomal abnormality of the embryo. However, a variety of other factors can contribute to continued failure to carry a pregnancy. In some cases, genetic factors can prevent an embryo from developing normally. In other cases, conditions affecting the uterus, metabolic causes, environmental factors, infections, hormonal disorders, and possibly clotting disorders can affect a woman’s ability to carry a pregnancy.
A genetic problem with a developing embryo or a genetic condition that affects one or both parents may result in recurrent miscarriages.
As many as 50-70% of all early pregnancy losses are believed to be caused by abnormalities in the chromosomal makeup of the embryo. These errors typically occur early in the oocyte (egg) maturation process and less commonly during sperm maturation.
In some cases, one or both parents may have a chromosomal abnormality, resulting in an embryo with too much or too little genetic material. We can evaluate a couple’s chromosomes with a test called a karotype analysis. While some genetic issues affecting parents are undetectable, we can now test embryos for certain genetic abnormalities before they are transferred back to the uterus during in vitro fertilization. This process is called pre-implantation genetic diagnosis (PGD).
The process of implantation is hormonally regulated and requires a synchronized interaction between the implanting embryo and the lining of the woman’s uterus (endometrium). Factors that alter this relationship can result in pregnancy losses.
The hormone progesterone, produced by the ovaries in the second half of a woman’s ovulatory cycle, is necessary for the establishment and maintenance of pregnancy. The relationship between the hormonal environment of early pregnancy and implantation is intricate and, not very well understood.
Anatomical or structural problems with a woman’s uterus, including polyps, fibroids, or congenital defects, can result in miscarriage or complications later in pregnancy. An ultrasound test (saline sonography) or an X-ray test (hysterosalpingogram, or HSG) can reveal many structural abnormalities of the uterus. Occasionally, additional imaging studies may be required. Fortunately, many abnormalities of the uterus can be corrected through surgery.
It is clear that there is a special relationship between the uterus and the immune system, but the exact nature of this relationship is not well understood at this time.
Two antibodies, lupus anticoagulant (LAC) and anticardiolipin antibodies (ACA) are believed to promote fetal death by causing clotting in the early placental circulation. Other classes of antiphospholipid antibodies have been investigated, but none have yet been found to be associated with recurrent miscarriages. Testing for ACA and LAC are performed on all recurrent pregnancy loss patients. Treatment involves the use of low dose aspirin and other anti-clotting medications.
Abnormalities of certain white blood cell functions have been proposed as a potential cause of miscarriage, but no meaningful data exists to support this as a cause of miscarriages. The field of immunology is evolving and our approach to screening and treatment may change as more scientific research becomes available.
Women who have had repeated miscarriages often ask about a link between miscarriage and environmental factors such as smoking, caffeine, and alcohol use and exercise. While some studies suggest that environmental factors may cause sporadic pregnancy loss, a link with recurrent pregnancy loss has not been firmly established. We generally advise all pregnant women, but especially those with a history of recurrent loss, to avoid smoking (including second-hand smoke exposure), excessive caffeine intake (more than two cups of coffee/day) and alcohol use. There is no evidence to suggest that exercise increases a woman’s risk of pregnancy loss. However, there are no studies suggesting that strenuous exercise is safe for recurrent loss patients. Therefore, as a precaution, we suggest that women avoid strenuous aerobic exercise. In addition, there is some evidence to suggest that women with a history of miscarriage should avoid exposure to biohazards, solvents or certain industrial chemicals that are known to have an effect on a developing fetus. Your doctor can help you evaluate your risk of exposure to these materials if this is a concern.
It is believed to be unusual for an infection to cause a miscarriage and it is extremely unlikely that infections cause multiple pregnancy losses. Some suspected but unproven infectious causes of pregnancy loss include the bacteria mycoplasma, ureaplasma and Chlamydia. Screening is done through cultures and we are typically able to eliminate those problems during the evaluation.
Diseases affecting the endocrine system, especially those that are relatively mild, do not appear to increase the risk of miscarriage. However, certain disorders, including uncontrolled diabetes or thyroid disease are known to increase a woman’s risk of miscarriage. In addition, women with Polycystic Ovary Syndrome are at increased risk for sporadic loss, but the condition has no proven association with recurrent pregnancy loss. Based on an individual’s health history, we may recommend an evaluation for an endocrine disorder. In many cases these conditions can easily be managed with medication and should be corrected prior to further attempts at conception.
Thrombophilias, the tendency to form blood clots, appear to be associated with a variety of problems in pregnancy, although studies are inconclusive. Research suggests a link between thrombophilias and pregnancy-related problems in the second and third trimester. These include fetal growth problems, fetal death, pregnancy-induced hypertension and placental separation. However, the association between thrombophilias and first trimester loss is controversial. Testing for thrombophilias is based on an individual’s health history. Most cases of thrombophilias can be treated with low dose aspirin and other anti-clotting medications.
For about one third of all couples that experience recurrent pregnancy loss, the cause is attributable to more than one factor. In these cases, multiple treatments may be required. However, for nearly half of all couples with recurrent pregnancy loss, no cause is revealed by the evaluation.
For couples with no evident cause of recurrent loss, studies suggest that chromosome abnormalities of the embryos are the most likely explanation. For these couples, as well as couples with known chromosome abnormalities, a technique called pre-implantation genetic diagnosis (PGD) used in conjunction with IVF may be beneficial. Using PGD, we can test embryos that have been grown in the laboratory for specific genetic abnormalities prior to transferring the embryos into the uterus. The goal of PGD is to reduce the risk of a miscarriage.
Overall, PGD appears to be safe and effective. However, like all treatments, there are limitations. Your physician can help you determine if PGD is right for you.
Recurrent pregnancy loss can be an emotionally difficult experience for couples that want to have a baby. In addition to treatment, many couples find that they benefit from emotional counseling and support services, as well as relaxation therapy. These helpful services are available at ARMG through our Complementary Care program. Fortunately, a thorough medical evaluation and proper treatment can, in many cases, help couples that experience recurrent pregnancy loss to have a successful pregnancy and birth. A majority of couples that experience three or more losses are eventually able to deliver a baby. A comprehensive evaluation and treatment of any identifiable causes of loss is essential for maximizing the chances for success.