['We tested the hypothesis that apoptotic trophoblasts from pregnancies associated with fetal growth restriction caused by preeclampsia or cigarette use exhibit enhanced expression of the proapoptotic proteins p53 and Bax and diminished expression of the antiapoptotic protein Bcl-2.', 'Placentas were obtained from women with uncomplicated pregnancies (n = 4) or from women with pregnancies complicated by fetal growth restriction associated with preeclampsia, cigarette use, or both (n = 7). Placental sections were examined by means of hematoxylin and eosin and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) staining, as well as by detection of cytokeratin 18 cleavage products indicative of apoptosis. The expression of p53 was examined by means of Western immunoblotting and immunohistochemistry. The expression of Bax, Bcl-2, Bak, and Bcl-X(L) was analyzed by immunoblotting.', 'More apoptosis was found in the trophoblast layer of villi from pregnancies complicated by fetal growth restriction than in the trophoblast layer of villi from control pregnancies. The enhanced apoptosis correlated with up-regulation of p53, primarily in cytotrophoblast nuclei. There was no difference between the two groups in expression of the proteins from the Bcl-2 family.'] Is trophoblast apoptosis from pregnancies complicated by fetal growth restriction associated with enhanced p53 expression?