Preterm birth seasonality in Greece: an epidemiological study

Objective: Seasonality of preterm birth has been noted, although not conclusively studied. Weather is also thought to play a role. We sought preterm birth seasonality and additionally studied the effect of weather parameters in the preterm birth pattern. Methods: Vital statistics from the Hellenic Statistical Authority were retrieved, covering the years from 1980 to 2008. Additionally, weather data were retrieved for the years of the study. Time series analysis was used to create various statistical models that would be compared to each other for their accuracy to predict preterm birth. Factors used in the modeling included month of birth, gender and weather factors. Results: Preterm birth seasonality was exhibited. Two peaks of higher risk of preterm birth were noted: One during summer and one during winter. Males were more influenced by seasonality and exhibited slightly different seasonal patterns than females, although no higher risk for preterm birth was noted. The best model that described seasonal pattern of preterm birth was the one that included meteorological factors. Notably, extreme (hotter or colder) weather was accompanied by an increase in preterm birth. Conclusions: Evidence for seasonality of preterm birth was shown and extreme weather was associated with a higher incidence of it.