Overview

Miscarriage is the sudden loss of a pregnancy before the 20th week. About 10% to 20% of known pregnancies end in miscarriage. But the actual number is likely higher. This is because many miscarriages happen early on, before people realize they're pregnant.

The term miscarriage might sound as if something was amiss in the carrying of the pregnancy. This is rarely true. Many miscarriages happen because the unborn baby does not develop properly.

Miscarriage is a somewhat common experience — but that doesn't make it any easier. If you've lost a pregnancy, take a step toward emotional healing by learning more. Understand what can cause a miscarriage, what raises the risk and what medical care might be needed.

Symptoms

Most miscarriages happen during the first trimester of pregnancy, which is about the first 13 weeks.

The symptoms can include:

  • Bleeding from the vagina with or without pain, including light bleeding called spotting.
  • Pain or cramping in the pelvic area or lower back.
  • Fluid or tissue passing from the vagina.
  • Fast heartbeat.

If you have passed tissue from your vagina, place it in a clean container. Then, bring it to your health care professional's office or the hospital. A lab can examine the tissue to check for signs of a miscarriage.

Keep in mind that most pregnant people who have vaginal spotting or bleeding in the first trimester go on to have successful pregnancies. But call your pregnancy care team right away if your bleeding is heavy or happens with cramping pain.

Causes

Irregular genes or chromosomes

Most miscarriages happen because the unborn baby doesn't develop properly. About half to two-thirds of miscarriages in the first trimester are linked with extra or missing chromosomes. Chromosomes are structures in each cell that contain genes, the instructions for how people look and function. When an egg and sperm unite, two sets of chromosomes — one from each parent — join together. But if either set has fewer or more chromosomes than usual, that can lead to a miscarriage.

Chromosome conditions might lead to:

  • Anembryonic pregnancy. This happens when no embryo forms. Or the embryo forms but is absorbed back into the body. The embryo is the group of cells that develops into an unborn baby, also called a fetus.
  • Intrauterine fetal demise. In this situation, an embryo forms but stops developing. It dies before any symptoms of pregnancy loss occur.

  • Molar pregnancy and partial molar pregnancy. With a molar pregnancy, a fetus doesn't develop. This most often happens if both sets of chromosomes come from the sperm. A molar pregnancy is linked with irregular growth of the placenta, the pregnancy-associated organ that gives an unborn baby oxygen and nutrients.

    With a partial molar pregnancy, a fetus may develop, but it can't survive. A partial molar pregnancy happens when there is an extra set of chromosomes, also called triploidy. The extra set is often contributed from the sperm but can also be contributed from the egg.

    Molar and partial molar pregnancies can't continue because they can cause serious health problems. Sometimes, they can be linked with changes of the placenta that lead to cancer in the pregnant person.

Maternal health conditions

In a few cases, having certain health conditions might lead to miscarriage. Examples include:

  • Uncontrolled diabetes.
  • Infections.
  • Hormonal problems.
  • Uterus or cervix problems.
  • Thyroid disease.
  • Obesity.

What does NOT cause miscarriage

Routine activities such as these don't cause a miscarriage:

  • Exercise, as long as you're healthy. But talk with your pregnancy care team first. And stay away from activities that could lead to injury, such as contact sports.
  • Sex.
  • Arguments.
  • Use of birth control pills before getting pregnant.
  • Working, as long as you're not exposed to high doses of harmful chemicals or radiation. Talk with your health care professional if you're concerned about work-related risks.

Some people who've had a miscarriage blame themselves. They think they lost the pregnancy because they fell, had a bad scare or other reasons. But most of the time, miscarriage happens because of a random event that is no one's fault.

Risk factors

Various factors raise the risk of miscarriage, including:

  • Age. If you're older than age 35, you have a higher risk of miscarriage than a younger person. At age 35, you have about a 20% risk. At age 40, the risk is about 33% to 40%. And at age 45, it ranges from 57% to 80%.
  • Past miscarriages. If you've had one or more prior miscarriages before, you're at higher risk of pregnancy loss.
  • Long-term conditions. If you have an ongoing health condition, such as uncontrolled diabetes, you have a higher risk of miscarriage.
  • Uterine or cervical problems. Certain uterine conditions or weak cervical tissues, also called incompetent cervix, might raise the chances of a miscarriage.
  • Smoking, alcohol, caffeine and illegal drugs. People who smoke have a greater risk of miscarriage than do nonsmokers. Heavy use of caffeine or alcohol use also raises the risk. So does using illegal drugs such as cocaine.
  • Weight. Being underweight or being overweight has been linked with a higher risk of miscarriage.
  • Genetic conditions. Sometimes, one of the partners may be healthy but carry a genetic problem that raises the risk of a miscarriage. For example, one partner could have a unique chromosome that formed when the pieces of two different chromosomes attached to each other. This is called translocation. If either partner carries a chromosome translocation, passing it to an unborn child makes a miscarriage more likely.

Complications

Sometimes, pregnancy tissue that stays in the uterus after a miscarriage can lead to a uterine infection about 1 to 2 days later. The infection is called a septic miscarriage. Symptoms include:

  • Fever higher than 100.4 degrees Fahrenheit more than two times.
  • Chills.
  • Pain in the lower stomach area.
  • Foul-smelling fluid called discharge from the vagina.
  • Vaginal bleeding.

Call your health care professional's office or your local OB triage or emergency department if you have these symptoms. The illness can get worse fast and become life-threatening without treatment.

Heavy bleeding from the vagina, called a hemorrhage, is another miscarriage complication. Along with the bleeding, a hemorrhage often happens with symptoms such as:

  • Fast heartbeat.
  • Dizziness from low blood pressure.
  • Tiredness or weakness due low red blood cells, also called anemia.

Get medical care at once. Some people who have a hemorrhage need blood from a donor or surgery.

Prevention

Often, there's nothing you can do to prevent a miscarriage. Instead, focus on taking good care of yourself and your unborn baby:

  • Get regular prenatal care while you're pregnant and right after you give birth.
  • Stay away from miscarriage risk factors — such as smoking, drinking alcohol and illegal drug use.
  • Take a daily multivitamin.
  • If you've had one or more prior miscarriages, ask your health care professional if you should take low-dose aspirin.
  • Limit caffeine. Many experts recommend having no more than 200 milligrams per day while pregnant. This is the amount of caffeine in a 12-ounce cup of brewed coffee. Also, check food labels for amounts of caffeine. The effects of caffeine aren't clear for your unborn baby and higher amounts may include miscarriage or preterm birth. Ask your pregnancy care team what's right for you.

If you have a long-term health condition, work with your health care team to keep it under control.

By Mayo Clinic Staff