This study examines the birth rates and the proportion of illegitimate births in Mörbylånga parish and Kalmar town before and during the period of the Contraceptive Act. The purpose of the study is to investigate what effect the Contraceptive Act may have had on birth rates and illegitimate births in the above-mentioned areas. The investigation period extends from 1880-1938 and the Prevention Act was in use 1910-1938. The study method is quantitative, and the results are presented using diagrams. The study also has comparative elements where an urban environment is compared with a rural environment. The demographic transition theory is used to interpret and analyze the results.  The study shows that birth rates in both Mörbylånga and Kalmar had an upward trend. In Mörbylånga, this trend is much clearer than in Kalmar, which shows that the increase in birth rates was higher in rural areas than in the city. It can not be ruled out that the advent of the contraceptive law is a factor that contributed to the increase in birth rates in these study areas. The results from this study also differ from previous research as their results show a decrease in birth rates and this study shows an increase. Other results are that a larger proportion of illegitimate children were born in rural areas than in the city over the entire survey period and that the proportion of illegitimate children decreased in both survey areas. Furthermore, it can be stated that the Contraceptive Act had some form of effect on the decline in the proportion of children born out of wedlock.