The fertility rate in Iran has recently changed significantly, to the point where Iran today faces a single-child phenomenon. The purpose of this study was to determine the role of demographic variables in the tendency for one child phenomenon of married women. In this study 200 married women participated whit a random sample selection from health centers. The inclusion criteria were to select married women who had one child and had at least 10 years of married life. The data collection instruments were a questionnaire to examine demographic variables (age, education, women's employment, etc.) in the tendency towards a phenomenon of one child. The results showed that more than 70% of participants did not consider one child to be ideal and only 32% tended to have one child. MANOVA test results showed that the tendency to have one child had a significance to education. Other results showed that only child planning and women's employment were correlated and forced to have one child. The overall conclusion is therefore that, while most women tend not to have one child, society's current conditions are such that women are forced to work, making them plan for the number of their children.