Miscarriage is the loss of a pregnancy after conception and implantation has occurred.
Miscarriages can be classified in a number of different ways. The most commonly used system involve how the pregnancy was verified before the loss was identified.
Biochemical pregnancy; Biochemical miscarriage, Chemical pregnancy, Early miscarriage
This is a miscarriage that occurs after a positive pregnancy test but before a pregnancy could be seen on ultrasound.
Clinical miscarriage, Clinical pregnancy
A miscarriage that occurs after or at the same time that it is seen on ultrasound. This is a very broad group. Some very early pregnancies can be detected by sensitive ultrasounds. There are four subcategories of clinical miscarriage that depend on what features were seen on the ultrasound:
- Gestational sac only
- Gestational sac and yolk sac
- A fetus is seen
- A fetus is seen with a heartbeat
Missed miscarriage, Missed abortion
A missed miscarriage is determined when an ultrasound shows a pregnancy is nonviable and the measurements or features suggest that it occurred a period of time before the ultrasound. For example, an obstetrician is unable to hear the fetal heart beat at 12 weeks gestation. An ultrasound is performed and the fetus is measured but it corresponds to an 8 week gestation.
Threatened miscarriage, Threatened abortion
Any bleeding that occurs in the first twenty weeks of pregnancy is defined as a threatened miscarriage. Approximately 1/2 of these pregnancies will go on to miscarry. However, if ultrasound has previously shown a fetus with a heartbeat a much smaller percentage (1-5% depending on the age of the female) will miscarry.
Incomplete miscarriage, incomplete abortion
A miscarriage that is in progress. Some of the fetal or placental tissue has passed but not all of it. Generally, the cervix is dilated.
Completed miscarriage, completed abortion
A miscarriage in which all of the fetal or placental tissue has passed.
Learn more about miscarriage