Interesting question! There are so many possible causes for a miscarriage. Most of them occur before the 12th week of pregnancy. Other miscarriages occur so early that the pregnant woman may not even notice she was even pregnant. In these cases they occur in the first two to three weeks of a pregnancy and are usually due to the lack of embryo implant or in other cases, there is no embryo, and the resultant miscarriage is early, but is not the loss of child, though it may still be an emotionally difficult time.
Although medical literature indicates that miscarriages are not caused by working, I think stressful situations at work can contribute to the loss of a pregnancy. Engaging in sexual intercourse, or exercising are not reasons or causes for a miscarriage, however, a woman with a history of more than one should probably refrain from intercourse or streneous exercise at least on the first trimester.
Miscarriages could be the result of:
1. Genetic abnormalities so severe that life is not sustainable in utero.
2. Failure for an embryo to form a functioning heart or brain due to genetic misfiring usually means fetal death. Often these abnormalities are not the result of known genetic causes in the parents.
3. There are some genetic disorders that may be carried by both parents, or one parent recessively, which can cause severe malformations and miscarriages. When a woman has had more than two miscarriages, obstetricians will often refer the couple to a genetic counselor to rule out a genetic cause.
4. Another cause of miscarriage is malformation or scarring of the uterus, which results in the inability for the unborn child to properly grow.
5. Some diseases may also cause miscarriage. Exposure to measles for a woman who is not immune can cause either miscarriages or severe malformation of an unborn child.
6. Chronic illnesses like diabetes and lupus have also been indicated in higher risk of miscarriage. Diabetes that is well controlled by medication carries a lower risk, but when the disease is uncontrolled the rate of both miscarriage and birth defects significantly increases. Lupus, an autoimmune disorder, can create a situation where normal cells that control immunity do not distinguish between germs and the body’s organs. This may cause the cells to attack the growing embryo, rendering it non-sustainable.
7. Other risk factors include smoking during pregnancy, using certain medications contraindicated during pregnancy, and use of illegal drugs.
8. Low progesterone levels during pregnancy can also result on the loss of the pregancy.
In most cases however, there is no identifiable cause, and women often feel mistakenly guilty for “causing” a miscarriage. Miscarriages taking place closer to the 20th week are more suspect, and an obstetrician may want to initiate testing to discover potential causes. More than two miscarriages usually call for investigation to help prevent future lost pregnancies.