Miscarriage Health Article

Definition

A miscarriage is the loss of an embryo or fetus before the twentieth week of pregnancy. A pregnancy loss after the twentieth week is called a stillbirth.

Description

According to the December 1999 news release from the U.S. government's National Center for Health Statistics, about 16% of recognized pregnancies end in miscarriage (i.e., prior to 20 weeks' gestation) or stillbirth (after 20 weeks' gestation). The medical term used for a miscarriage is spontaneous abortion, or early pregnancy loss. Most miscarriages occur during the first trimester of pregnancy. However, the statistics are unclear for the total number of recognized and unrecognized miscarriages in the United States. This is because a number of recognized miscarriages go undetected. When the pregnancy loss occurs early, the woman may not have missed her period yet. In this instance, she would not be aware of the pregnancy loss. Medical attention would not have been sought, and no statistic would have been generated.

Causes and symptoms

Causes of miscarriage may be genetic, anatomic, endocrinologic, infectious, immunologic, or exposure to a toxin. About 50–60% of first-trimester miscarriages occur as a result of a chromosomal abnormality, which renders the fetus non-viable. A definitive cause for the loss of a pregnancy cannot always be determined, as the products of conception (POC) are often passed by the woman at home or at work; they have not been collected for pathologic examination. The chromosomal abnormality is usually of spontaneous origin, a mutation that is not repeated in a subsequent pregnancy that continues to term.

A woman with a malformed uterus (e.g., bicornate) or cervix is also at increased risk for miscarriage. Women whose mothers took the medication diethylstilbestrol (DES) while they were in utero are especially likely to have suffered reproductive tract anomalies. The presence of fibroids can compete with the fetus for space and blood supply, and may result in miscarriage.

In about 17% of cases, a miscarriage is hormonal in nature, such as with insufficient secretion of progesterone, which results in a luteal phase insufficiency. Polycystic ovarian syndrome (PCOS), thyroid dysfunction, and poorly controlled diabetes mellitus are other hormonal causes of miscarriage.

Bacterial vaginosis, which may be present in as many as 31% of pregnant women, has been shown to increase the risk of miscarriage two fold, although it does not appear to affect a woman's ability to conceive. Individuals with a compromised immune system, causing them to be more susceptible to infectious organisms, are at increased risk of miscarriage. Toxoplasmosis can also cause miscarriages. The age of the egg at the time of fertilization may also be a factor. The older the egg, relative to ovulation, may be at greater risk of pregnancy loss.

Toxins and other workplace hazards that may increase the risk of miscarriage include:

• smoking, where the risk increases with each 10 cigarettes smoked daily
• caffeine, as in coffee, when four or more cups are consumed daily
• alcohol
• exposure to arsenic, lead, formaldehyde, benzene, and ethylene oxide
• multiple pregnancy, as in the case of carrying twins
• treatment with anticancer drugs, such as methotrexate
• exposure to ionizing radiation

The most common sign that a pregnancy is in danger is vaginal bleeding. The amount can vary from very light to heavy. The color of the blood varies as well, from brown to bright red. However, bleeding in early pregnancy is relatively common, and does not necessarily indicate impending miscarriage. One in four or five pregnant women experience bleeding in early pregnancy. Many women have some bleeding at the time of implantation, which occurs seven to 10 days after conception. Because of the possibility of pregnancy loss, any bleeding during pregnancy should be immediately reported to a woman's health care provider. The blood may be clotted, containing visible pieces of tissue. Bleeding may also be a sign of ectopic pregnancy, where the egg implants in a location other than the uterus, 95% of the time in a fallopian tube. Growth of the fertilized egg can lead to rupture of the tube, and can be life-threatening to the mother if untreated.

Cramping is another sign of a possible miscarriage. Cramping occurs as the uterus tries to expel the POC. The woman may also experience pain, dull and unrelenting, or sharp and intermittent, in the lower abdomen or back. When pain and bleeding persist, miscarriage is most likely to occur.