Placental apoptosis in normal human pregnancy

OBJECTIVES: The study aims were to conclusively demonstrate apoptosis in the human placenta and to quantify its incidence at different stages of pregnancy. STUDY DESIGN: Placental samples were obtained from 28 first-trimester pregnancies and 38 uncomplicated third-trimester pregnancies. Light microscopy, electron microscopy, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate marker nick end-labeling staining were used to identify apoptosis. Light microscopy was used to quantify its incidence. RESULTS: Apoptosis has been conclusively demonstrated within placental tissue. Quantification of apoptosis (medians and interquartile ranges) was as follows: first trimester (n = 28), 0.07% of cells (0.05% to 0.14%); third trimester (n = 39), 0.14% of cells (0.09% to 0.20%). The incidence of apoptosis was significantly higher in the third trimester than in the first trimester (p < 0.01, Mann-Whitney U test). CONCLUSIONS: Placental apoptosis increases significantly as pregnancy progresses, suggesting that it may play a role in the normal development and aging of the placenta.