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Miscarriage: Risk Factors, Treatment and Prevention of Pregnancy Loss

Miscarriage is defined as a spontaneous pregnancy loss that occurs before twenty weeks of gestation, i.e., before the fetus is considered viable. In medicine, this is referred to as spontaneous abortion. It is estimated that ca 25% of known pregnancies end in miscarriage. However, the actual rate is believed to be yet higher because many miscarriages occur early in pregnancy, before a woman may realize that she is pregnant.

Types of Miscarriage

  • Threatened miscarriage. A woman has vaginal bleeding and sometimes also abdominal pain early in pregnancy, but her cervix has not begun to dilate. This does not automatically imply that a miscarriage will occur. Often, the bleeding subsides and the pregnancy continues to term.
  • Inevitable miscarriage. A woman has vaginal bleeding accompanied by contractions of her uterus and dilation of the cervix.
  • Complete miscarriage. A woman has a miscarriage and none of the tissue from the pregnancy remains in her uterus. Bleeding and cramping after the miscarriage resolves without medical intervention.
  • Incomplete miscarriage. A woman has expelled most of the pregnancy tissue through her vagina (e.g., fetus), but some remains in the uterus (e.g., pieces of the placenta). The cervix remains open and bleeding may be heavy, often requiring some intervention.
  • Missed miscarriage. Also known as missed abortion, occurs when the fetus died prior to the twenty weeks of gestation, but neither the fetus nor placenta were expelled by the uterus. Interventions may be offered but often the tissue may be spontaneously expelled. In this case, a woman is usually not aware of the pregnancy loss.
  • Septic miscarriage. A miscarriage is accompanied by an infection in the uterus.
  • Recurrent miscarriage. Also known as recurrent pregnancy loss, occurs when a woman experiences the loss of two or more consecutive pregnancies in the first or second trimester or the loss of three or more pregnancies before twenty weeks gestation.
  • Blighted ovum. This condition occurs when a gestational sac forms inside a woman’s uterus, but no fetus is present after seven weeks. It usually happens very early in pregnancy before a woman may know she is pregnant.
  • Molar pregnancy. This is a rare condition which occurs when a pregnancy results in the growth of abnormal tissue (benign tumor) rather than an embryo. Molar pregnancy typically ends in miscarriage before the fourth month of pregnancy.

Causes and Risk Factors for Miscarriage

The causes of miscarriage are not yet thoroughly understood but scientists believe that the majority of miscarriages occurring in the first twelve weeks of pregnancy (in the first trimester) are a result of random chromosomal abnormalities in the fetus. Chromosomal abnormalities are also believed to be responsible for nearly 50% of recurrent miscarriages. These randomly occurring events surface during cell division and are not inherited from the genes of either parent. Chromosomal problems may also result in a blighted ovum, either because the embryo did not form or because it stopped developing very early.

Other medical conditions that may cause miscarriages are:

  • Uterine and/or cervical abnormalities. They can be congenital or acquired (e.g., scars from past surgery or noncancerous growths). Uterine and cervical abnormalities can interfere with the blood supply to the uterus or limit space for the fetus to grow or affect the ability for the embryo to implant properly. These structural abnormalities are estimated to account for 10-15% of recurrent miscarriages. Some can be surgically corrected to improve the chances of a future pregnancy.
  • Hormonal abnormalities. When the body produces too little or too much of certain hormones, a miscarriage may occur. Conditions associated with hormonal abnormalities that may result in a miscarriage include polycystic ovarian syndrome, thyroid disease and luteal phase defect.
  • Chronic diseases. Women with autoimmune disorders such as systemic lupus erythematosus, intrauterine infections, uncontrolled diabetes mellitus, congenital heart disease, thyroid disease and severe kidney disease are at a higher risk of miscarriage. Patients with any of these conditions should get proper treatment to control them before becoming pregnant.
  • Immune system disorders. Certain types of autoantibodies can attack the body’s own tissues in some people (e.g., those with lupus or antiphospholipid antibody syndrome), causing a variety of health problems that may result in miscarriage.
  • Infections. Infectious diseases that have been associated with causing miscarriage include listeriosis, toxoplasmosis, herpes, measles, mumps, rubella, syphilis and HIV, among others.
  • Fever. Pregnant women who develop fevers of 38 degrees Celsius or more (100.4 degrees Fahrenheit) may increase their risk of miscarriage.
  • Blood incompatibility. Sometimes, when the fetus’ and mother’s blood type do not match (Rh incompatibility), the mother may develop antibodies to the fetus and spontaneous abortion may occur.
  • Previous miscarriages. Women with a history of recurrent miscarriage have an increased risk of miscarriage.

Other factors associated with a higher rate of miscarriage include:

  • Age. Women over 40 are at increased risk of miscarriage and recurrent miscarriage compared with younger women as chromosomal abnormalities become more common with aging. But the partner’s age also plays a role because genetic quality of sperm gradually deteriorates as men get older, increasing a man’s risk of fathering unsuccessful pregnancies.
  • Number of pregnancies. Women who have had two or more pregnancies appear to have a higher risk of miscarriage.
  • Folate insufficiency. Pregnant women with inadequate levels of folic acid (vitamin B9) are at greater risk of miscarriage.
  • Low body weight. Underweight women are more likely to suffer a miscarriage during the first trimester.
  • Alcohol. Drinking alcohol during pregnancy increases the risk of miscarriage by 100%. In addition, alcohol may harm the development of the fetus, even when miscarriage does not occur and, as a result, cause low-birth weight and birth defects such as fetal alcohol syndrome.
  • Use of certain medications or substances. Taking certain prescription and over-the-counter drugs, including NSAIDs like ibuprofen and illegal narcotics increases a woman’s risk of miscarriage.
  • Smoking. Smoking more than ten cigarettes a day is associated with greater risk of miscarriage and can be harmful to the developing fetus even in cases where miscarriage does not occur.
  • Trauma. Severe trauma to the uterus from a fall or serious accident may increase the risk of miscarriage. This, however, does not include activities of daily living, such as working or lifting heavy objects, exercising or sex, which usually do not provoke a miscarriage.
  • Environmental factors. Exposure to environmental toxins such as arsenic, lead, mercury, benzene, formaldehyde, ethylene oxide as well as large doses of radiation or anesthetic gases may also cause a miscarriage.
  • Use of donor eggs. Women who achieve pregnancy via assisted reproductive technology using donated eggs may be more likely to experience miscarriage. This is due to a negative immune system reaction against the foreign egg.
  • Prenatal testing. Certain types of prenatal genetic tests, such as amniocentesis or chorionic villus sampling, are associated with a slightly increased risk of miscarriage because of the invasive nature of these procedures.

Symptoms of Miscarriage

Symptoms of a miscarriage may include vaginal bleeding or spotting, pelvic pain or painful cramping in the abdomen or lower back and fluid or tissue being expelled from the vagina. Although vaginal bleeding is a symptom that usually precedes almost all pregnancy losses, it is not always indicative of a miscarriage. Many pregnant women experience spotting or bleeding at some point during their pregnancies. Additional symptoms of a miscarriage may include frequent bowel movements, weight loss and decreasing signs of pregnancy.

Diagnosing Miscarriage

If a miscarriage is suspected, a doctor will review a full medical history and perform a thorough pelvic examination. The aim of this exam is to check the size of the uterus and determine whether the cervix is open or closed. Furthermore, a doctor may use an ultrasound scan to establish if a miscarriage has occurred or to help determine if the pregnancy is capable of progressing to term. Blood tests can also be ordered to monitor the course of pregnancies that are complicated by bleeding.

Doctors usually do not perform any tests following a first miscarriage that occurs in the first trimester because the cause of these early losses is often unknown (chromosomal abnormalities mentioned earlier are usually suspected). But, if a miscarriage occurs during the second trimester or in case of recurrent miscarriage, the following tests may be ordered to determine the cause:

  • Karyotype test to check for chromosome abnormalities in the mother and her partner.
  • Transvaginal ultrasound to find abnormalities in the vagina, uterus, ovaries, fallopian tubes, bladder and other nearby tissues.
  • Hysterosalpingography to look for blockages and other problems in the uterus and fallopian tubes.
  • Hysteroscopy to view the uterus and treat causes of abnormal bleeding. It is usually prescribed if results from the hysterosalpingography were abnormal.
  • Sonohysterography to make images of the uterine cavity in order to determine uterine and/or cervical abnormalities that may cause recurrent miscarriages.
  • Magnetic resonance imaging to confirm uterine abnormalities after a transvaginal ultrasound or hysterosalpingography.
  • Endometrial biopsy to determine if the uterine lining is sufficiently hospitable to allow the embryo to implant and grow.
  • Analysis of tissue samples to examine chromosomal abnormalities in tissue from the miscarriage.

Treatment Following a Miscarriage

Treatment of a miscarriage that seems inevitable or is already occurring includes several options depending on the stage of the miscarriage, the symptoms and the condition of the mother. These may include:

  • Observation. Most often, women who miscarry do not need further medical treatment because the uterus usually empties itself within a couple of weeks. An ultrasound is then performed to ensure that the miscarriage is complete. If not, any remaining pregnancy tissue must be removed to prevent infection.
  • Medication. In some cases, medications, such as misoprostol, may be given to stimulate the uterus to expel remaining pregnancy tissue.
  • Surgery. A dilation and curettage is a surgical procedure used to treat early miscarriage with incomplete dispelling of the uterus. In this procedure, the cervix is dilated and an instrument is inserted that uses gentle scraping motion or suction to remove the contents of the uterus.

In case of recurrent miscarriage, further treatment may be recommended, such as:

  • Surgery to correct uterine or cervical abnormalities.
  • Hormone therapy. Human menopausal gonadotrophin (hMG) hormone or clomiphene citrate may be prescribed to stimulate ovulation in women with luteal phase deficiency.
  • Hormone progesterone may also be administered to prevent miscarriage due to luteal phase deficiency. However, some studies suggest that this treatment is not without a risk and there is no conclusive evidence yet to support the effectiveness of this treatment.
  • Rh (D) immune globulin is prescribed in the case of Rh incompatibility to help protect future pregnancies against problems such as miscarriage.

Following a miscarriage, a woman will be advised to maintain pelvic rest (no sexual intercourse or inserting tampons into the vagina) for up to two weeks and to wait for three months before attempting to conceive again. Medications may be prescribed to help reduce bleeding and infection.

Preventing Miscarriage

Since most miscarriages are caused by chromosomal abnormalities, a miscarriage is in most cases not the fault of the mother and, therefore, there is little that can be done to prevent it. However, all women should have yearly check-ups with their obstetrician-gynecologist to monitor their reproductive health. In addition, women who are trying to become pregnant should take a good care of themselves. This includes exercising regularly, eating a well-balanced diet, taking folic acid supplements, maintaining a healthy weight, managing stress and refraining from drinking alcoholic beverages and smoking.

Furthermore, if a woman is already pregnant, it is also important to receive good prenatal care by an obstetrician, always check with a doctor before taking any medications, refrain from activities that have risk or injury, avoid raw foods that may contain harmful bacteria, avoid unnecessary radiation and x-rays and get proper treatment for chronic illnesses that may increase the risk of miscarriage.

Where to Find More Information: American Pregnancy Association