BACKGROUND: Chinese New Year is the biggest festival in Chinese culture and the holiday season includes January and February. People have to change their life patterns to celebrate this traditional holiday, so embryo transfer during this holiday season may be affected. METHODS: This is a retrospective cohort to analyze IVF outcomes by month. The primary outcome is the live birth rate. Data were analyzed by multivariate logistic regression. Propensity score matching (PSM) data and inverse

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... lity of treatment weighting (IPTW) data were analyzed as sensitivity analysis. RESULTS: Totally 4,688 patients were recruited. Of 4,449 women in the non-holiday season group, 1,930 had live birth (43.38%), while 77 of 239 women in the holiday season group had live birth (32.22%), p<0.001. Multivariate logistic regression showed that holiday season (OR=0.62, 95%CI 0.47-0.82, p=0.001), age (OR=0.50, 95%CI 0.42-0.60, P<0.001), number of oocytes retrieval (OR=1.17, 95%CI 1.09-1.25, p<0.001) E2 (OR=0.86, 95%CI 0.75-0.98, p=0.026), T (OR=1.14, 95%CI 1.01-1.28, p=0.036), and AMH (OR=1.15, 95%CI 1.01-1.32, p=0.036) were independent factors associate to live birth. PSM data analysis showed the live birth rate in the holiday season group is 31.78%, while 42.64% in the non-holiday season group, p=0.005. IPTW data also showed that the holiday season had a lower live birth rate than the non-holiday season (OR=0.64, 95%CI 0.47-0.87, p=0.005). CONCLUSIONS: This research demonstrated the existence of a previously unknown decline in the live birth rate during the Chinese New Year holiday season. Celebrations along with overindulgence may have contributed to this decline.