The aim of this paper was to investigate seasonal fluctuations of the number of births in Croatia. Vital registration
data from the years 1970–2002 was used for analysis of the quarterly data (from the years 1970–1997), and monthly
data (from the years 1998–2002). Both data sets were smoothed, using seasonal variation removal for quarterly data,
and T4253H smoothing for monthly data. Edwards test and Ratchet circular scan tests were used in analysis. The results
showed an increase in the summer birth proportion and decrease in the spring birth proportion, distorted during
the wartime period (1991–1995). Monthly analysis reveals highest birth proportion in Croatia during July–September
period, with peak date moving towards the end of summer, and reaching stability in the beginning of September during
the years 2000–2002. This presumes highest conception rate during the beginning of the Christmas holiday season.
Secondary peak in January was found in some years, which presumably sets second period of increased conception
rate into the Easter holiday season, supporting the observation of the holiday-related birth peaks. Both quarterly and
monthly data indicate a birth pattern that does not resemble either »European« or »American« seasonal pattern. Regional
analysis showed lack of seasonality in the capital city of Zagreb and either intermittent or stable seasonality
pattern in the rest of the country.