The invention provides pharmaceutical compositions for treating male sub-fertility including an agent that causes a reduction in an effect of extracellular DNA on sperm cells. 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. The invention also provides methods for treating male sub-fertility comprising administering a pharmaceutical composition of the invention. The invention further provides 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.
