Couples' experience of living with infertility is influenced by social values and scientific norms arising from the dominant model of modern medicine. the predominance of the bio-medical model Since the 19th century, and the division of diseases according to the cause of their occurrence, categorized infertility, along with other diseases, as a physical phenomenon which its treatment relies on finding its causes. this research was due to study the lived experience of "infertile couples with unexplained infertility disorder" as a 15% minority who despite having enough potential, do not have children. 22 under-treatment-couples in Royan Institute were participated. In this paper, descriptive phenomenology and 7-step Claizian analysis method were used. The findings were categorized in 13 clusters and 3 categories which include: approaches (the perception of infertility, the perception of being unexplained in infertility, the perception of parenthood as a role, the perception of treatment and the perception to a child), experiences (experience of pressure, experience of sexual relationship, experience of marital relationship and experience of terminated parenting) and fundamental structures (the issue of time, existing possibilities, gender and fatalism). Finally, the central phenomenon of " to be on threshold" explains the lived experience of "infertile couples with unexplained infertility disorder" which refers to observing an uncontrollable situation in which couple with a juxtaposed sense of ambiguity and desperation are willing to reach a level of certainty.