Each year, between 600,000 and 800,000 U.S. women miscarry. Given that a woman is likely to have more than one pregnancy, the chances that she will have a miscarriage at some time in her life are very great. Miscarriages are a possible outcome of first as well as subsequent pregnancies, even after a woman has given birth to many full-term normal children. It is related to age--the likelihood of miscarrying is high for very young teenagers, reaches its lowest point (12 percent) for women around the age of 20, and increases to 41 percent for women pregnant at the age of 42. They are more common in early (between the seventh and fourteenth week of gestation) rather than late (between the fifteenth and twenty-eighth week) stages. Miscarriage is also a highly likely outcome of pregnancies accomplished with the assistance of reproductive technology.
Because people often believe erroneously that miscarriages do not occur after the first trimester, some women do not divulge the fact that they are pregnant during that time. People are also superstitious about miscarriages and do not like to talk about them with pregnant women. As a result, pregnant women frequently know very little about them.
Currently women receiving prenatal care who are at risk for miscarriage are prescribed bedrest, reduced activity and cessation of sexual intercourse, although none of these prohibitions has been definitely linked with increasing the chances of averting miscarriage.
The likelihood of a subsequent miscarriage increases after two experiences. Repeat miscarriages can sometimes be traced to a cause (e.g., genetic abnormality or exposure to teratogens) that may be correctable. The cause of most miscarriages is not known, although most probably reflect a defect in the developing fetus rather than a problem in the woman or her partner. Male fetuses are more likely to be miscarried than female fetuses.
-Encyclopedia of Childbearing: Clinical Perspectives, edited by Barbara Katz Rothman PhD, Oryx Press, 1992
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Fifteen percent of all clinically recognized pregnancies end in miscarriage. When pregnancy is diagnosed much earlier with very sensitive hormone tests, it is found that up to 60% of pregnancies end in miscarriage. Considering this figure of 15%, we would expect only 0.4% of women to miscarry 3 times consecutively, and it be due to nothing more than chance. In fact, 0.8-1.0% of women do so, suggesting other factors may be involved.
It is important to remember that 60-75% of women who have recurrent miscarriage (RM) will go on to have a successful pregnancy the next time, without tests or treatment. When a woman is investigated for RM, the majority of the time no cause is found.
Following are some of the things which are thought to be associated with RM:
-Systemic Lupus Erythematosus (SLE) which is a disease affecting many systems of the body. People affected often have a butterfly-rash over the cheeks and bridge of the nose.
-Antiphospholipid antibody syndrome. This is an immune disease where the main problems are RM, clots in the veins or arteries and often a low platelet count. If pregnancy is successful, it can be complicated by poor growth of the baby and preeclampsia.
-Chromosome problems. Parents are fine, but when put together an unusual gene mismatch occurs (only 3% of RM).
-Uterine (womb) abnormality. Double-womb or a septum down the middle, associated in about 4% of RM and is found in 1.8-3.6% of the normal population. Whether this type of problem actual is to blame hasn't been proven, and the risks of surgery to correct the problem must be weighed against any potential benefit.
-Fibroids sometimes cause misshaping of the womb cavity.
-Cervical incompetence (weakness). May cause miscarriage in 2nd trimester, but only likely if there is clear history of severe or recurrent trauma to the cervix with RM. Some women are just born with a weak cervix. This is not as common as some people report, and the diagnosis is very difficult to make.
-Polycystic ovary syndrome. Often this disease causes infertility or trouble even getting pregnant. When it is present with a raised hormone level (LH) there is an increased risk of miscarriage. Hormonal treatment for this is being looked into, but there is minimal evidence available on who might benefit. It does appear that women with very irregular periods and a raised LH may benefit.
-Immune problems. Couples with RM may have some similar components of the immune system. This can make it difficult for the woman to make the appropriate response to pregnancy. This is a controversial finding, and no immune therapy has been found to improve chances above and over the 60-75% seen without intervention.
-Hormone "deficiency": In pregnancies that end in miscarriage, sometimes the levels of progesterone are found to be low. This is thought to reflect an early pregnancy failure, and is probably the *result* rather than the cause of the miscarriage. Progesterone supplements do not increase the likelihood of an ongoing pregnancy.
-D.E. Tucker, Women's Health, www.womens-health.co.uk
Reprinted from Midwifery Today E-News (Vol 1 Issue 43, Oct 22, 1999)
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