What Is the Definition of a Miscarriage or Pregnancy Loss?

Pregnant woman wearing green dress resting in bed
Katja Kircher/Getty Images

What Is the Definition of a Miscarriage?

Pregnancy loss refers to the unexpected loss of an unborn baby. It can occur for any number of reasons, most of which have little or nothing to do with the activities of the mother or any other party. Doctors and patients do not generally use the term “pregnancy loss” to refer to the intentional ending of an unwanted pregnancy.


Generally, pregnancy losses fall into one of four categories: miscarriage, stillbirth, birth loss, and medically based termination.

The most common is a miscarriage, which refers to any pregnancy loss that takes place before the 20th week in pregnancy (pregnancy typically lasts 40 weeks). The majority of miscarriages happen even earlier than that -- usually before the 12th week or by the end of the first trimester.

Researchers believe that miscarriages are most frequently the result of random genetic problems in the developing baby. Miscarriages may also be the result of a condition such as an ectopic pregnancy, where the fertilized egg begins to develop outside the uterus, causing medical risks that lead to a medical termination. In other cases, the cause is an undetected medical issue. In still other cases, it is impossible to determine a cause.


The term stillbirth refers to any loss after 20 weeks in which the baby is not alive at birth. Sometimes doctors can find a medical cause for stillbirths, and sometimes a cause is never determined.

The most common causes of stillbirths are problems with the placenta and genetic conditions in the baby.

Birth Loss

In other cases, a baby may be born alive but extremely premature due to a medical issue in the mother such as cervical insufficiency, where the cervix begins to dilate and the woman goes into labor before the baby is ready to be born.

Medical advances have led to increased survival rates for babies born early, but generally if a baby is born before 24 weeks, the odds of survival are fairly low even though the baby may be born alive.

Medically Indicated Termination

A final category of pregnancy loss is the termination of a wanted child for medical reasons. For example, the mother may develop a medical condition that would make it life threatening for her to continue a pregnancy and she may have to terminate the pregnancy, or the developing baby may be found to have a genetic condition such as Trisomy 18 (which leads to death shortly after birth in many cases), and the parents may opt to terminate rather than continue the pregnancy.

Aftermath of a Pregnancy Loss

Regardless of the category, pregnancy losses are often emotionally devastating, sometimes carrying deep psychological impact for the mother and father, and support is often crucial for getting through the experience.

Because most pregnancy losses are random occurrences and the couple can usually go on to have a normal pregnancy the next time, doctors do not normally complete medical testing following a single loss. When pregnancy loss occurs two or more times in a row, doctors label it “recurrent pregnancy loss,” or recurrent miscarriage (this usually happens in earlier losses rather than stillbirths or genetically based terminations).

You should discuss recurrent miscarriages with your medical practitioner, because sometimes the mother (or father) may have a treatable medical condition contributing to the losses.

If someone you know has miscarried, it might be hard to know what to say, even if you want to be supportive. If you can, consider offering to help out around the house while your loved one is grieving. The most important thing is to make sure that your friend or family member knows you are there and willing to listen.

Bleeding and Severe Cramping

If you are experiencing miscarriage symptoms, call your medical practitioner as soon as possible for guidance.

Spotting and vaginal bleeding do not always lead to a miscarriage, but if you are bleeding, you should go in for an evaluation. Depending on how far along you are in the pregnancy, your practitioner will most likely perform blood tests or an ultrasound in order to get more information about what is going on.

If you are experiencing severe pain on one or both sides of your abdomen, then head to the nearest emergency room in order to rule out ectopic pregnancy.


A.D.A.M., Inc., "Miscarriage." 19 Sept. 2006. A.D.A.M. Healthcare Center. [Online]. Accessed 6 Oct 2007.