This retrospective observational study examined whether fasting (the 'Yom Kippur effect') precipitates labour. Birth rates of Yom Kippur (a fasting festival) were compared with those of other festivals that are observed (Tisha B'Av) and not observed (1st day of Passover) by fasting during a 4-year period. Compared with the mean birth rate, the number of births that occurred 1 day after Yom Kippur was increased (p = 0.023). A significant decrease in the number of births during Tisha B'Av (p = 0.044) and a significant increase in the number of births 2 days after Tisha B'Av (p = 0.009) was observed. Two days prior to the 1st day of Passover, a significant decrease in the number of births was also observed (p = 0.034). Contrary to previous reports, the present study does not confirm an association between a 1-day long fast and increased birth rate in the 24-h period after breaking of the fast.