A miscarriage (also termed spontaneous abortion) is any pregnancy that spontaneously ends before the fetus can survive. Any vaginal bleeding, other than spotting, during early pregnancy is considered a threatened miscarriage. Vaginal bleeding is very common in early pregnancy. About one out of every four pregnant women has some bleeding during the first few months. About half of these women stop bleeding and complete a normal pregnancy.

Miscarriage is the most common type of pregnancy loss, according to the American College of Obstetricians and Gynecologists (ACOG). Studies reveal that anywhere from 10-25% of all clinically recognized pregnancies will end in miscarriage. Chemical pregnancies may account for 50-75% of all miscarriages. This occurs when a pregnancy is lost shortly after implantation, resulting in bleeding that occurs around the time of her expected period. The woman may not realize that she conceived when she experiences a chemical pregnancy.

Some miscarriages occur before women recognize that they are pregnant. About 15% of fertilized eggs are lost before the egg even has a chance to implant (embed itself) in the wall of the uterus. A woman would not generally identify this type of miscarriage. Another 15% of conceptions are lost before eight weeks' gestation. Once fetal heart function is detected in a given pregnancy, the chance of miscarriage is less than 5%.

Symptoms of Miscarriage

The most common symptom is vaginal bleeding, which can range from light spotting to heavier than a period. You may see blood clots, brown discharge or other tissue that is not clearly identifiable. Sometimes a sac-like structure is seen.

Pain you may have pelvic cramps, abdominal pain, or a persistent, dull ache in your lower back. Pain may start a few hours to several days after bleeding has begun.

Some women experience cramping, spotting, abdominal pain, fever, weakness, vomiting, or back pain. Spotting is not always a sign of a miscarriage; many women normally experience it early on in pregnancy. But just to be safe, if you have spotting or any of these other symptoms anytime during your pregnancy, it's a good idea to talk with your doctor.

Sometimes there are no signs or symptoms of miscarriage and pregnancy symptoms continue, and the miscarriage is only discovered in a routine scan.

Causes of Miscarriage

An abnormal fetus causes almost all miscarriages during the first three months of pregnancy (first trimester). Problems in the genes are responsible for an abnormal fetus and are found in more than half of miscarried fetuses. The risk of defective genes increases with the woman's age, especially over if she is older than 35 years.

Apart from abnormal fetal development, a number of other factors can contribute to a miscarriage. These may include abnormalities in the father's sperm; abnormalities in the egg; disease in the mother (for example, an infection, a glandular disorder, high blood pressure, kidney or heart disease, or diabetes); uterine abnormalities; the mother's poor nutrition or use of cigarettes, alcohol, or drugs; and exposure to pollutants.

Chromosomal abnormalities also become more common with aging, and women over age 35 have a higher rate of miscarriage than younger women. Advancing maternal age is the most significant risk factor for early miscarriage in otherwise healthy women.

Exposure to environmental and workplace hazards such as high levels of radiation or toxic agents. Incompetent cervix (the cervix begins to widen and open too early, in the middle of pregnancy, without signs of pain or labor).