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A missed abortion, which is also often called a missed miscarriage, occurs when the pregnancy is not viable, but the embryo has not yet been expelled from the uterus. Many women who experience this type of miscarriage are not aware of it until their doctor cannot find a heartbeat for the embryo. Until this point, the pregnancy may appear to be continuing as usual, with no abnormal bleeding or cramps. In most cases, the only way to detect signs that a missed abortion may have occurred is to get an ultrasound.
The typical signs of a miscarriage are usually absent during a missed abortion. For example, most women notice light spotting at the beginning of a spontaneous abortion, often followed by heavy bleeding with passage of tissue. They also usually notice severe cramping and pelvic pain, as well as a sudden loss of normal pregnancy symptoms. In most missed abortions, there is no sign of blood or abnormal pain, and most of the pregnancy symptoms may still be present. For this reason, most women are not aware that a missed abortion has taken place.
Of course, it usually becomes obvious during a visit to the doctor, especially when an ultrasound is included in the appointment. The first sign that the pregnancy is not viable is the absence of a heartbeat in the embryo. In some cases, it is too early in the pregnancy to pick up a heartbeat, requiring the woman to come back within a few weeks for another ultrasound. On the other hand, if the heartbeat was found before, and can no longer be detected, it is likely that a missed abortion has occurred. Additionally, if the embryo seems large enough to be at least six weeks old, the typical doctor will rule it a missed miscarriage if there is no heartbeat.
There are other signs of a missed abortion that a doctor can look for, with the main one being lack of growth since the last appointment. If neither the embryo nor its gestational sac has grown at all within about a week, the pregnancy is likely not viable. Also, a yolk sac that is either oddly shaped or particularly large may indicate that the pregnancy has continued without the embryo, which may be why the body has not expelled any tissue or blood. This could also explain why most pregnancy symptoms are often still present despite the lack of a living embryo.