Miscarriage is common and usually due to a genetically abnormal conceptus, uterine anomalies, abnormal clotting or immunology of pregnancy implantation; miscarriage prevention is also discussed at Florida Institute for Reproductive Medicine in Jacksonville, FL
A miscarriage is defined as a pregnancy loss before the 20th week of development. After the 20th week a pregnancy loss is referred to as an intrauterine demise. Miscarriages are extremely common, most women whether they know it or not have had 2-4 losses some time during their reproductive life. Frequently when a woman is a week late for her period and then begins to bleed she has had a miscarriage. The great majority of miscarriages are early occurring before seven weeks. Most of these early losses are due to pregnancies that are genetically abnormal. We believe in most cases that these abnormal embryos result from an abnormal egg coming in contact with sperm. In most cases we believe it is the egg that is genetically incorrect because the egg is so much older than the sperm. A female is born with a certain number of eggs, she never makes any more eggs. Eggs accumulate genetic/chromosomal errors as a function of time. Men in contrast continue to make new sperm all their lives. Sperm are no more than about 90 days old when they die. There is a slight increase incidence of genetically abnormal sperm in males above the age of 50, but it is slight.
Definitions of pregnancy.
Reproductive medicine specialists refer to three different definitions of pregnancy: 1) chemical pregnancy, an early pregnancy determined by a positive pregnancy test either urine or blood. This pregnancy has not reached the point where gestational material can be visualized on ultrasound. 2) clinical pregnancy, is a pregnancy that has developed to the point where gestational material can be visualized on ultrasound. 3) ongoing pregnancy, is a pregnancy that has continued past 20 weeks.
Causes of miscarriage.
The earlier the pregnancy loss the more likely it is due to a genetically abnormal conceptus. Most genetically abnormal pregnancies occurred because of the chance ovulation and fertilization of an abnormal egg with a normal sperm. There are individuals who are carriers of genetic conditions which will cause all or an increased percentage of their sperm and eggs to be abnormal. One of the most common examples of this is a balanced translocation, whereby both parents both have the correct genetic material, but because of the way the chromosomes are structured a certain percentage of their sperm or eggs will be abnormal and will result in a miscarriage. If a woman is age 42 or above miscarriage rates can be as high as 50-70%. Beyond ten weeks of gestation causes other than genetic become increasingly common including: anatomic, clotting disorders or immunologic conditions. These conditions are important to identify as they are frequently treatable.
Problems with the uterus supporting a pregnancy include: the presence of polyps (exaggerated overgrowths of the endometrial lining), fibroid tumors (firm, benign growths), scarring of the endometrial surface, the presence of endometrial tissue in the wall of the uterus (adenomyosis), as well as developmental problems with the uterus, i.e., the presence of a uterine septum, an absence of uterine volume, i.e. a unicornuate, bicornuate or uterine didelphis anatomy. With some of these abnormalities surgery can be performed to improve pregnancy outcome.
Abnormal clotting conditions.
Individuals may be born or acquire abnormal clotting disorders. These abnormal clotting factors are collectively known as antiphospholipid antibodies (APA). APA can impair the microcirculation of the placenta resulting in early or late losses. An individual who has had repeated losses with consistently elevated APAs is said to have antiphospholipid antibody syndrome. Treatment for antiphospholipid antibody syndrome consists of baby aspirin and heparin or lovenox.
Immunologic pregnancy loss.
Very little information is known about the immunology of pregnancy implantation. It is known that every pregnancy is genetically different than the host, i.e., as a result of half the genetic material being provided by the male partner. The body has a mechanism by which this genetically different material is not rejected known as “blocking antibodies”. For some patients there seems to be a defect in blocking antibody production that results in repeated losses. A history of autoimmune disease, arthritis, thyroiditis, unexplained rashes should raise suspicion of an immune problem. Over the last three decades there have been a multitude of studies addressing immunologic pregnancy loss, unfortunately diagnosis and treatments of these conditions have been inconsistent and expensive. If an individual is suspected of having an immunologic cause for pregnancy loss they should consider enrollment in a valid study protocol, usually through a tertiary referral educational program – there should be minimal or no costs associated with such therapy.