What complication is characterized by a fertilized egg implanting outside the uterus?

The complication characterized by a fertilized egg implanting outside the uterus is ectopic pregnancy. In this condition, the fertilized egg typically attaches to a fallopian tube, though it can occur in other areas such as the ovary or abdomen. This situation poses significant risks, as the developing embryo cannot survive outside the uterine cavity, and the pregnancy can lead to serious health complications for the individual, such as internal bleeding, if the ectopic tissue ruptures.

In contrast, miscarriage refers to the loss of a pregnancy before the 20th week, typically occurring within the uterus. Placenta previa involves the placenta covering the cervix, which can cause complications during delivery but does not pertain to the implantation site of the fertilized egg. Labor dystocia indicates a difficult labor process due to various factors but does not relate to the implantation of the egg at all. Thus, the defining characteristic of ectopic pregnancy is directly associated with the abnormal implantation behavior of the fertilized egg, making it the correct answer.