The work presents some preliminary results of a research project on variations and determinants of secondary sex ratios in Italy. Variations in sex ratios at birth is still an active research field and several studies focus on this topic. Early works stated that the human sex ratio at birth was universally stable, without significant fluctuations across time and space. However, in the last decades various authors directly challenged these conclusions. After reviewing these studies on the historical trends of the sex ratio at birth, long term tendencies in Italy are analyzed. We collect historical and contemporary series of sex ratios at birth, covering more the 160 years, and compare them with those of different European countries. In this work, studies on the main determinant of long- and short-term trends are briefly reviewed, taking into account findings and results from different kinds of disciplines. The variations in the sex ratio at birth mentioned in the literature are assessed by using birth series at the national and regional level. Compared with other industrialized countries, sex ratio trends in Italy occurred with some delays. Intrauterine and fetal mortality appeared to be a key factor in sex ratio variations.
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