The persistent sub-replacement fertility levels in most developed and some developing countries, including Iran, have remained a concern for policy makers. Low fertility has been largely linked to increasing opportunity costs of childbearing for women, gender inequality in the family, and the spread of individualism, whereas the fertility influence of transformations in the spousal intimate relationship has remained understudied. Drawing on the four qualities of the concept of “pure relationship”, coined by Anthony Giddens, a survey questionnaire was designed and conducted in a representative sample of 400 prospective grooms and brides, residing in the city of Tehran, Iran, to test the hypothesis that partners supporting egalitarian intimate relationships, having a greater “risk profile” attached to their intimate relationships, evaluating frequently their relationship against alternative choices and possibilities, and having less attachments to the external normative pressures and factors shaping marital relations, are more likely to intend to have one or no children, state one or zero as an ideal number of children, and postpone childbearing long. Using data from the survey and multivariate logistic regression models, this study found evidences that support the hypothesis. The results shed a new light on the causes of persistent below-replacement fertility rates.