Approximately 15% of pregnancies end in miscarriage, which is defined as the loss of a pregnancy before 20 weeks of gestation. The majority of miscarriages occur within the first 12 weeks of gestation. 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. It is important to know that the overwhelming majority of women will go on to have a live birth after having one or even two miscarriage(s), although some women require treatment to improve odds of live birth and diminish risk for miscarriage.
Symptoms of recurrent miscarriage
Symptoms for recurrent miscarriage are not more severe than those for a single miscarriage. If a woman experiences any of the following symptoms while pregnant, she should seek medical attention immediately:
- Vaginal bleeding
- Passing fetal tissue
- Cramping and pain in the abdomen
- Fever
Causes of recurrent miscarriage
Pinpointing the cause of repeated miscarriages can be difficult. In more than half of couples with recurrent pregnancy losses doctors are unable to find a specific reason. Yet there are a number of factors at play. Below are causes of Recurrent pregnancy loss(RPL) and their related diagnosis and treatment options.
Age
Age increases the chance of a miscarriage. Age-related pregnancy loss is associated with poor egg quality, which leads to genetic abnormalities. More than one-third of all pregnancies after age 40 end in miscarriage.
The best available technique for assessing the quality of a woman’s eggs is measuring what’s known as ovarian reserve, determined by levels of Anti-mullerian hormone, and follicle stimulating hormone (FSH) and estradiol. In some cases a clomiphene challenge test is performed in women over the age of 38 who have a solitary ovary or have had a prior poor response with fertility medications. These tests will determine if aggressive therapy is indicated and how successful we will be at attaining a pregnancy using a woman’s own eggs.
Genetic factors
Chromosomes play a factor in such cases of advanced maternal age, as most embryos that end in miscarriage for these women carry an abnormal number of chromosomes.
Recurrent pregnancy loss due to chromosomal abnormalities affects approximately 3-8 percent of all pregnancies. For both natural and assisted conception, chromosomally abnormal embryos have a low rate of implantation in the uterus. The most common genetic cause of RPL is aneuploidy, the presence of an extra chromosome or the absence of one in the normal pair of chromosomes. Down syndrome, also known as trisomy 21, is the presence of an additional 21st chromosome and is a common form of aneuploidy.
Environmental factors
Environmental exposures could affect the outcome of a pregnancy. Some anesthetic agents and tetrachoroethylene used in dry cleaning have been associated with miscarriages. If proper precautions are used, including a mask respirator and specialized clothing, then the exposure is minimal and should not cause a problem.
Additionally, several reports have shown a strong association between smoking and pregnancy losses. The risk increases with the number of cigarettes smoked per day.
Exposure to aspartame (an artificial sweetener found in a variety of beverages and used as a sugar substitute in brand name products such as Equal and NutraSweet), heavy caffeine and alcohol intake have all been associated with pregnancy loss. But scientists have not defined the exact amount. Therefore, we advocate limiting the intake of these items while trying to conceive and avoiding these during pregnancy.
Endocrine problems
An endocrine problem is found in 15 percent of women who have RPL. Any hormonal imbalance that affects ovulation could impair normal uterine lining development, and ultimately implantation. Thyroid disease or pituitary dysfunctions are the most common findings associated with RPL due to endocrine issues. Women with an elevated luteinizing hormone (LH) level, as with polycystic ovary syndrome (PCOS), may be at increased risk of miscarriage due to an increased amount of male hormones that adversely affects the uterine lining.
Anatomical Causes
Uterine anomalies are found in 12-15 percent of woman with pregnancy losses and also contribute to RPL. These abnormalities include fibroid tumors, derived from the muscle wall of the uterus, or polyps(, overgrowths of the uterine lining).
Congenital uterine malformations, such as a uterine septum, are associated with a 60 percent pregnancy loss rate (see below). Surgical correction by operative hysteroscopy has been reported to provide an 80 percent delivery rate.
Incompetent cervix is a condition in which the cervix opens prior to 20 weeks gestation without detectable contractions. In these women, the use of cervical cerclage, a suture placed in the cervix, at the end of the first trimester may reduce the risk of a pregnancy loss.
Uterine anomaly percent risk for a pregnancy loss are as follows:
- Septate – 60 percent
- Unicornuate – 35 percent
- Bicornuate – 33 percent
- Didelphic – 29 percent
- DES exposure – 28 percent
Blood clotting abnormalities
Abnormalities in blood clotting function resulting from chromosomal anomalies are also a potential cause of pregnancy losses and RPL.
Thrombophilia is one of these conditions where there is tendency for increased blood clotting, and may be treated with a baby aspirin, heparin anticoagulant injections and/or an increased amount of folic acid.
Antiphospholipid syndrome (APS or APLS) may cause 3-15 percent of RPL in women. APS is also a coagulation disorder that causes thrombosis in both arteries and veins and can lead to miscarriages, pre-term delivery or severe preeclampsia, a serious threat to both maternal and infant health.
Immunologic Factors
Blood clots in the small placental blood vessels may be due to the antibodies lupus anticoagulant and anticardiolipin that attach to the wall of the blood vessel and attract clotting factors that can impede blood flow. The result is placental insufficiency and possible miscarriage. Treatment with aspirin and/or heparin anticoagulant injections does not guarantee improvement but studies have reported success rates approaching 85 percent for most women.
Determining treatment for recurrent miscarriage
If testing after two consecutive miscarriages suggests an underlying problem, then treatment is directed in one or more of several directions which may be in the form of : genetic counseling, removal of polyps or fibroids, hormonal correction and anticoagulation. If all of the tests are normal then the diagnosis is recurrent miscarriage of unknown cause.
Repetitive losses are frustrating and can cause depression as well as family discord. One often-overlooked factor of tremendous importance is the psychological impact. Along with medical treatment, we encourage counselling to help cope with the emotional aspects of recurrent miscarriage.
