Objective: To determine whether there are differences in the expression of progesterone receptor (PR) in intermediate trophoblastic cells of pregnancies ending in either spontaneous abortion (SAB) or elective abortion.
Design: Immunohistochemical identification of PR in intermediate trophoblastic cells.
Setting: Academic medical center.
Patient(s): Subjects were 86 patients who either underwent first trimester SAB or elective abortion.
Intervention(s): All SAB and elective abortion specimens were serially sectioned and immunohistochemically stained for PR and for melanoma cell adhesion molecule. Melanoma cell adhesion molecule immunohistochemical staining was used as a sensitive and specific marker to identify intermediate trophoblastic cells on the adjacent tissue section.
Main outcome measure(s): The PR staining of intermediate trophoblastic cells by semiquantitative immunostaining score.
Result(s): The PR expression in intermediate trophoblastic cells was significantly greater in elective abortion specimens than in SAB specimens. When controlling for estimated gestational age, the difference in PR expression was even greater.
Conclusion(s): The quantity of PR in intermediate trophoblastic cells is significantly less in SAB when compared to elective abortion pregnancies. Although it is unknown whether this is a primary or secondary event, this information may be an important finding in attempting to characterize both the molecular etiology of implantation and the molecular pathophysiology of SAB.