Apoptosis is a rare event in first-trimester placental tissue

Objective: The aim of this study was to confirm our previous findings of an increase in the incidence of placental apoptosis with increasing gestational age by means of transmission electron microscopic assessment of first-trimester placental tissue. We also wanted to challenge the validity of terminal uracil nick end–labeling staining for the assessment of placental apoptosis. Study Design: The incidence of apoptosis was quantified with hematoxylin and eosin staining and terminal uracil nick end–labeling staining in 6 first-trimester placental samples, 5 second-trimester placental samples, and 7 third-trimester placental samples. These results were then compared with the results that were obtained by quantifying apoptosis in 6 first-trimester placental samples with transmission electron microscopy. Results: Our previous hematoxylin and eosin–staining findings of a rise in apoptosis with increasing gestational age were confirmed. Transmission electron microscopy confirmed the low incidence of apoptosis in first-trimester placental tissue. Terminal uracil nick end–labeling staining produced incongruous results. Conclusion: Our earlier findings of a low incidence of apoptosis in first-trimester placental tissue have been confirmed by transmission electron microscopy, which remains the criterion standard in the assessment of apoptosis. Our findings discredit terminal uracil nick end–labeling staining for the assessment of placental apoptosis. (Am J Obstet Gynecol 2000;183:697-9.)