Examination of the early conceptus.

The pathologist encounters the early, first-trimester conceptus as a product of spontaneous or surgical abortion or as a specimen from ectopic, usually tubal, gestation. In the vast majority of cases of spontaneous abortion, the embryo/fetus has been dead for 1 week to several weeks and is most often lost in the process of uterine emptying; the placenta, accordingly, stands as the main "witness" of the abortive process. The fact of embryonic/fetal death is established and dated through an interpretation of gross and microscopic changes in the villous stroma, including its vessels and the embryonic erythrocytes therein. Elective abortions performed for social reasons occasionally yield abnormal findings that suggest gestations otherwise destined to eventual spontaneous abortion. Other therapeutic abortions are indicated by abnormal sonographic or cytogenetic findings that may be correlated with the morphologic features of the evacuated conceptus. Cytogenetic abnormalities correlate to a high degree with embryonic growth disorganization and with early death, usually before the fetal stage (30 mm) is reached. Adequate sampling of the placenta, its membranes, and of the embryo/fetus is recommended. For cytogenetic studies, clean, viable specimens must be obtained; these are most often required in cases of habitual abortion.