Annual Distribution of Births in the Province of Ferrara, Italy: A 15-Year Retrospective Study

Background: The distribution of births throughout the year is a widely documented phenomenon in epidemiological and demographic fields, with birth patterns following cyclic distributions characterized by recurring peaks and troughs. In high-income countries, a progressive dampening of the seasonal variation amplitude has been observed in recent decades, despite the persistence of temporal asymmetries. Aim: This study aimed to evaluate how factors like medical intervention impact maternal biological rhythms by analyzing monthly and seasonal trends in total vs. complicated births at Ferrara University Hospital. Methods: This retrospective study evaluated the monthly and seasonal temporal distribution of births recorded at the Ferrara University Hospital during the period 2005–2019. The analysis included the calculation of the observed/expected case ratio and Cosinor modeling. The analysis was conducted on both total deliveries and complicated deliveries. Results: A total of 23,235 deliveries were analyzed during the study period. Analyses including the Cosinor model highlighted a non-random monthly distribution, with a minimum in the spring months and a peak between September and October. In contrast, no statistically significant distribution was found on a monthly or seasonal basis for complicated deliveries. Conclusions: Our study revealed a clear seasonal pattern in total births, peaking in September–October and dropping to a minimum in spring. However, this natural annual seasonality disappeared in complicated births that required medical intervention, suggesting healthcare interventions may disrupt normal female physiological cycles.