Most miscarriages occur before the 12th week of pregnancy.
Signs and symptoms of a miscarriage might include:
- Vaginal spotting or bleeding
- Pain or cramping in your abdomen or lower back
- Fluid or tissue passing from your vagina
If you have passed fetal tissue from your vagina, place it in a clean container and bring it to your health care provider's office or the hospital for analysis.
Keep in mind that most women who experience vaginal spotting or bleeding in the first trimester go on to have successful pregnancies.
Abnormal genes or chromosomes
Most miscarriages occur because the fetus isn't developing normally. About 50 percent of miscarriages are associated with extra or missing chromosomes. Most often, chromosome problems result from errors that occur by chance as the embryo divides and grows — not problems inherited from the parents.
Chromosomal abnormalities might lead to:
- Blighted ovum. Blighted ovum occurs when no embryo forms.
- Intrauterine fetal demise. In this situation, an embryo forms but stops developing and dies before any symptoms of pregnancy loss occur.
Molar pregnancy and partial molar pregnancy. With a molar pregnancy, both sets of chromosomes come from the father. A molar pregnancy is associated with abnormal growth of the placenta; there is usually no fetal development.
A partial molar pregnancy occurs when the mother's chromosomes remain, but the father provides two sets of chromosomes. A partial molar pregnancy is usually associated with abnormalities of the placenta, and an abnormal fetus.
Molar and partial molar pregnancies are not viable pregnancies. Molar and partial molar pregnancies can sometimes be associated with cancerous changes of the placenta.
Maternal health conditions
In a few cases, a mother's health condition might lead to miscarriage. Examples include:
- Uncontrolled diabetes
- Hormonal problems
- Uterus or cervix problems
- Thyroid disease
What does NOT cause miscarriage
Routine activities such as these don't provoke a miscarriage:
- Exercise, including high-intensity activities such as jogging and cycling.
- Sexual intercourse.
- Working, provided you're not exposed to harmful chemicals or radiation. Talk with your doctor if you are concerned about work-related risks.
Various factors increase the risk of miscarriage, including:
- Age. Women older than age 35 have a higher risk of miscarriage than do younger women. At age 35, you have about a 20 percent risk. At age 40, the risk is about 40 percent. And at age 45, it's about 80 percent.
- Previous miscarriages. Women who have had two or more consecutive miscarriages are at higher risk of miscarriage.
- Chronic conditions. Women who have a chronic condition, such as uncontrolled diabetes, have a higher risk of miscarriage.
- Uterine or cervical problems. Certain uterine abnormalities or weak cervical tissues (incompetent cervix) might increase the risk of miscarriage.
- Smoking, alcohol and illicit drugs. Women who smoke during pregnancy have a greater risk of miscarriage than do nonsmokers. Heavy alcohol use and illicit drug use also increase the risk of miscarriage.
- Weight. Being underweight or being overweight has been linked with an increased risk of miscarriage.
- Invasive prenatal tests. Some invasive prenatal genetic tests, such as chorionic villus sampling and amniocentesis, carry a slight risk of miscarriage.
Some women who miscarry develop a uterine infection, also called a septic miscarriage. Signs and symptoms of this infection include:
- Lower abdominal tenderness
- Foul-smelling vaginal discharge