A miscarriage is the spontaneous abortion of an unborn child prior to the 20th week of pregnancy. Causes for a miscarriage are numerous. Frequently, miscarriages occur before the 12th week of pregnancy, and about 20-30% of pregnancies end in miscarriage. Some miscarriages occur so early that the pregnant woman may not even notice she has been pregnant. These tend to occur in the first two to three weeks of a pregnancy, and usually are due to the lack of the embryo to implant. 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 for parents.

Miscarriages are not caused by working, engaging in sexual intercourse, or by exercising. In some cases, those with past miscarriages may be asked to refrain from such to increase the likelihood of a pregnancy reaching term. Yet in most cases, these normal behaviors have no effect whatsoever on the developing child.

Miscarriages can also be caused by genetic abnormalities so severe that life is not sustainable in utero. 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. Conception and formation of a child is a hugely complex process from a genetic standpoint. Genes must come together, specialize and then dictate all the processes that will create a person. In some cases, genes make mistakes, and the result can be a miscarriage.

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.

Another cause of miscarriage is malformation or scarring of the uterus, which results in the inability for the unborn child to properly grow. If more than one miscarriage has occurred, and there have been no full-term pregnancies, resulting in a live birth, the obstetrician may perform examinations like ultrasounds to see if the uterus is properly formed. In severe cases, this may be determined by a regular examination. Often, however, ultrasounds, or magnetic resonance imaging (MRI) is needed to rule out uterine malformation, and may show a surgically correctable problem.

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. Frequently, now, a woman who wants to get pregnant has her immunity tested to determine whether she needs to be re-vaccinated for measles. If a new vaccination is required, the woman may have to wait a few months before trying to get pregnant.

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 escalates. 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.

Further risk factors are smoking during pregnancy, using certain medications contraindicated during pregnancy, and use of illegal drugs. In most cases however, there is no identifiable cause, and women often feel mistakenly guilty for “causing” a miscarriage. Guilt is often worse because women experiencing a miscarriage are at the same risk for postpartum depression as women who have had a complete pregnancy resulting in a healthy child. Both loss and guilt, however, are reasons enough to feel depressed and may be exacerbated by the loss of pregnancy hormones.

Since there are such a high number of miscarriages, a first miscarriage may not be cause for investigation, particularly if it takes place prior to the 12th week of pregnancy. 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.