What Are the Causes of Miscarriage?

There are multiple possible causes for a pregnancy ending unsuccessfully. Although not all the possible causes have been identified, we've listed the most common possible contributors to this serious problem.

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Genetic.  Perhaps half of all early miscarriages occur because of chance chromosomal abnormalities. Chromosomes carry the genes that hold the keys to your baby's traits. Most chromosomal abnormalities result from a defective egg or sperm, which produces an embryo with the wrong number of chromosomes or a chromosomal defect. These embryos often fail to thrive and the pregnancy miscarries.

Immunological. German measles or an infection accompanied by a very high fever may lead to a failed pregnancy. Women with a bacterial vaginal infection have a significantly greater risk of miscarriage in the second trimester of pregnancy.

Some women may have an inherited tendency to produce immune system antibodies that cause an excessive tendency to form blood clots, which can block circulation to the developing fetus. Women with these blood coagulation disorders have more failed pregnancies and pregnancy problems than other women.

Anatomical. If your cervix (neck of the uterus) is weak, it may start to open as the uterus becomes heavier in later pregnancy and this could lead to problems. An irregular-shaped uterus may not allow enough room for your baby to grow. Large fibroids in your uterus may cause miscarriage in later pregnancy.

Lifestyle. More than two alcoholic drinks a day may increase your risk. Smoking is a clear risk for abortion, premature birth, and low birth weight.

Stress.  Not only do PCOS women have a more difficult time becoming pregnant, they also have a higher rate of miscarriage. There is a simple way to reduce the probability of this heartbreak: Reduce your level of stress.

Chronic stress is a very important but overlooked factor in polycystic ovary syndrome and all of its related problems.

A recent study from the University of Michigan has discovered an association between miscarriage and levels of maternal urinary cortisol during the first 3 weeks after conception. Cortisol is a stress hormone that is produced in response to stress.

Too much of the stress hormone cortisol may contribute to early pregnancy loss. Excess cortisol is generally destructive to your body and contributes to abdominal obesity.

Source: Nepomnaschy PA et alCortisol levels and very early pregnancy loss in humans, Proc Natl Acad Sci U S A. 2006 Mar 7;103(10):3938-42

Diet. Some studies have suggested that coffee or caffeine may increase pregnancy complications.

What you eat can also affect your pregnancy outcome. One recent study has shown that women with low folic acid levels were 50% more likely to have a miscarriage than women with high levels. Folic acid is a B vitamin found most commonly in leafy green vegetables. Low zinc has also been associated with miscarriage. These studies imply that a poor-quality diet may be a contributor to pregnancy problems.

Eating a diet a low-fiber diet that is also high in refined carbohydrates and other processed foods will disturb your hormonal balance and could contribute to a higher risk of miscarriage. In particular, you want to avoid sweets and refined flour products, since these foods cause excessive increases in insulin.

These and other dietary issues relating to miscarriage are fully described in The Natural Diet Solution for PCOS and Infertility.

Environmental Pollution. Chemical compounds are everywhere in our food, water and air. Every person is a "bioaccumulator" of these chemicals. Some of these chemicals are hormone mimics or hormone disrupters. Others are just plain toxic. Women with high blood levels of a class of chemicals called "organochlorine compounds", have problems with infertility, stillbirths, and miscarriages.

There's no question that you have environmental chemicals in your fat tissue. The only question is what concentrations of chemicals do you have, and what effect are they having?

Hormonal. Women with hormonal irregularities may find it harder to conceive and when they do, they appear more likely to miscarry. A dominant feature of women with polycystic ovary syndrome (PCOS) is that they are likely to have multiple hormonal imbalances -- some are too high while others are too low.

Luteal phase defect. The luteal phase is the second half of your menstrual cycle, the time between ovulation and onset of the next menses. A luteal phase defect is essentially a failure of the uterine lining to be in the right phase of development at the right time, thus preventing implantation of the fertilized egg, or making the embryo's attachment to the uterus precarious.

A luteal phase defect may occur at several points during a menstrual cycle. It's thought that most luteal phase defects originate in the follicular phase of your cycle, before ovulation.

During the follicular phase, your body may not produce enough FSH (follicle stimulating hormone), or your ovaries have a weak response to FSH. The consequence is inadequate follicle development. After the follicle releases its egg, it converts itself into a different structure called the corpus luteum.

The corpus luteum produces the progesterone needed to thicken the lining of your uterus and stimulate development of additional blood vessels, which provide a place for your embryo to attach and to grow.

However, poor follicle formation will lead to a poor quality corpus luteum, and thus the corpus luteum is less likely to secrete the amount of progesterone required to ensure that the uterus can support the development of your embryo.

A luteal phase defect may also be caused by excessive levels of LH (luteinizing hormone) too early in the menstrual cycle, or an improperly timed LH surge.

LH (luteinizing hormone) hypersecretion. Some women with PCOS have elevated LH during the follicular phase (first half of the cycle), which prematurely sends a signal to the egg that it is about to be released from its follicle. The egg then prematurely disconnects from its supporting cumulus cells, which causes the egg to pause in its maturation process.

It is thought that this interruption in the normal maturation process may result in abnormal chromosomes in the egg, which would then substantially increase the probability of a miscarriage.

Other Hormones. Of course, other hormonal imbalances besides FSH and LH may be involved.

Women who miscarry appear to have higher levels of testosterone and DHEA than women with continuing pregnancies.

Women who miscarry may tend to have higher prolactin and androgen levels during the follicular phase of their menstrual cycle.

Insulin and insulin resistance. Some women with polycystic ovarian syndrome have insulin resistance, where an excessive amount of insulin is required to control blood sugar levels. High insulin levels stimulates further production of LH and testosterone. Excessive levels of insulin, LH and testosterone are associated with poorer egg quality, thus increasing the risk of miscarriage. Insulin resistance has been linked to recurrent pregnancy loss.

Insulin resistance and blood sugar problems can lead to the onset of diabetes during your pregnancy. This is called "gestational diabetes", a risk for both you and your unborn child. Read Brooke's exciting story of how she defeated gestational diabetes and had a successful pregnancy!

As you can begin to see, the risk of miscarriage may be increased by a complex, interacting web of hormones that are out of balance.

Cardiovascular.  Another possible cause is your cardiovascular system.

Researchers at the University Magna Graecia in Italy compared 73 pregnant women with PCOS and 73 pregnant women who did not have PCOS.  They measured the flow of the artery that supplies blood to the uterus during pregnancy.  They discovered that the PCOS group had reduced or abnormal blood flow to the uterus, which substantially increased the risk of pregnancy problems.

What might be a reason for the abnormal blood flow?

Women with polycystic ovary syndrome are more likely to have a condition called "endothelial dysfunction".  Endothelial dysfunction means that the cells in your artery walls are not working properly.  This condition is an "early warning" sign of future, more serious cardiovascular problems such as atherosclerosis (hardening of the arteries).

What might you do about it?

Eat a healthier diet.  Avoid unhealthy fats and eliminate all refined sugars from your diet. (If you don't know what an unhealthy fat is, read the "Fats and Oils" section of The Natural Diet Solution for PCOS and Infertility ebook.

Of course, regular exercise is highly advisable.

There are also certain nutritional supplements that may help.  For example, a report from the University of Indiana School of Medicine indicates that L-carnitine can reduce endothelial dysfunction in some people, especially if they have a weight problem.

Related Articles

Palomba S et al, Uterine blood flow in pregnant patients with polycystic ovary syndrome: relationships with clinical outcomes, BJOG. 2010 Mar 12. [Epub ahead of print]
Shankar SS et al, L-carnitine may attenuate free fatty acid-induced endothelial dysfunction, Ann N Y Acad Sci. 2004 Nov;1033:189-97

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