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Uterine expression of leukemia inhibitory factor (LIF) is absolutely essential for mouse, and critical for human, embryo implantation. However LIF is not required for post-implantation development of mouse embryo. The objective of this study was to examine the role of LIF system in post-implantation stage of human pregnancy.Tissues from 25 patients with anembryonic pregnancy (AP; blighted ovum) and 25 matched patients with normal pregnancy (NP) were collected. LIF and its receptor β (LIF-Rβ) expression in the decidua and chorionic villi were analyzed by semi-quantitative reverse transcription and polymerase chain reaction (RT–PCR), real-time quantitative PCR and immunohistochemical study.LIF mRNA levels were not different either between different tissues (decidua vs chorionic villi) or between different patients (NP vs AP). LIF-Rβ mRNA levels were significantly higher in chorionic villi than in decidua but were not different between NP and AP. Immunohistochemical staining supported these findings and showed a predominate expression of LIF-Rβ in the trophoblast cells.This study concluded that at early human post-implantation stage, LIF is produced from both decidua and chorionic villi and may exert its major action on trophoblasts. A baseline expression of LIF and LIF-Rβ is probably needed for early pregnancy, but AP cannot be accounted for by the defective expression of either LIF or LIF-Rβ in most circumstances.