Placental immunohistochemical analysis of cleaved PARP, caspase-3 and cytosolic cytochrome-c (number of positive cells counted) and the ratios of cleaved PARP, caspase-3 and cytosolic cytochrome-c positive cells in the spongy trophoblast layer of tumour-bearing rats or rats injected with ascitic fluid compared to control rats at different stages of pregnancy (16th, 19th and 21st days). The gene discussed is CASP3; the disease is neoplasm.