Introduction: Premature or preterm birth is a major problem around the world and in Slovenia as well. The average age of first-time mothers has been noticeably rising, and consequently, the intervals between pregnancies are shorter. Purpose: The purpose of the thesis is to provide theoretical knowledge on the problem of premature birth in Slovenia and worldwide. Short intervals between pregnancies also have an impact on premature birth incidence and, therefore, the goal of the thesis is to determine whether a connection exists between these two. Methods: The theoretical section of the thesis includes a critical overview of foreign and domestic scientific literature on the topic. In the empirical section, statistical data and statistical analysis of data from the National Perinatal Information System of the Republic of Slovenia are presented. We analysed data acquired from the Ljubljana Maternity Hospital for the period from 2002 to 2014. The criteria for inclusion in the study were multiple labours (two or more), a period of less than 77 weeks (18 months) between labours, newborn birth weight more than 500 g and liveborn infants. We studied the correlation between the incidence of premature labours and the length of intervals between pregnancies. Results: In the analysed period, there were 77,872 labours in the Ljubljana maternity hospital, 39,447 (50.65%) of which included second-time mothers. In the case of 10,200 women, the intervals between pregnancies were shorter than the period of 77 weeks. When comparing longer and shorter intervals between pregnancies, incidence of preterm birth was not significantly associated with shorter interval (828 (8.1 %) vs. 2770 (9.5%); odds ratio (OR) 1.194; 95% confidence interval (CI) 1.101- 1.295). Similarly, there was no association between shorter inter-pregnancy interval and very preterm birth (< 32 weeks) (207 (2.0%) vs. 749 (2.6%); OR 1,278;95% CI 1,094- 1,493). Discussion and conclusion: In the Ljubljana Maternity Hospital, from the year 2002 to 2014, there were 10,200 women who gave birth prematurely with a time period of less than 18 months (77 weeks) between labours. Based on our research, we cannot conclude that inter-pregnancy interval < 77 week is associated with higher incidence of preterm birth as was shown in previous studies. Further research is, therefore, needed to determine the optimal inter-pregnancy interval for preterm birth risk reduction in Slovenian population.