OBJECTIVE: To detect expression of connexin43 in cumulus cells and compare the differences between poor and non-poor ovarian responders undergoing in vitro fertilization (IVF), and to determinate whether the expression of connexin43 correlates with pregnancy outcome. STUDY DESIGN: A total of 152 infertile women undergoing IVF were included in this study. Patients were divided into 2 groups: poor ovarian responders and non-poor ovarian responders. Cumulus cells were collected from oocytes and were analyzed by Western blot for connexin43. Meanwhile, clinical data were obtained. RESULTS: The incidence of poor ovarian response was 18.42% (28/152). Connexin43 was detected in the cumulus cells of all the patients. The relative quantity of connexin43 in the poor responder group (1.11 [0.34, 2.11]) was much lower than that of the non-poor responder group (2.68 [1.41, 4.96]). There was significant difference in connexin43 between pregnant women and non-pregnant women. When adjusting for ovarian response, it yielded similar results. CONCLUSION: Expression of gap junction protein correlates with quantity of oocytes retrieved and might be related to pregnancy outcome. This study suggests that lack of connexin43 expression may contribute to poor ovarian response.