Pharmaceutical compositions for treating male sub-fertility that include an agent that causes a reduction in an effect of extracellular DNA on sperm cells, are provided. The agent may be, for example, an enzyme that degrades DNA such as DNase, a substance that blocks the interaction between cell free DNA and sperm cell surface receptors, a substance that binds to DNA, a substance that inhibits endogenous sperm cell DNase, a substance that inhibits a member of a signal transduction pathway mediated by DNA binding to sperm cell surface receptors, or an agent that stimulates production of an endogenous substance that causes a reduction in an antifertility effect of cell free DNA on sperm cells. Also provided are methods for treating male sub-fertility by administering the pharmaceutical composition to a subject in need thereof. Further provided are methods for determining a fertility status in a male subject, methods for assisted reproduction, methods for selecting an assisted reproduction technique (ART), and methods for selecting sperm cells in a sperm cell population for use in an assisted reproduction technique.