Potential causes of infertility are many and varied. Either the male or female partner may have an issue that renders conception impossible or highly unlikely. In perhaps one-third of cases, diagnostic procedures identify problems in both partners. Sometimes exhaustive testing fails to identify a cause in either partner. Oligoovulation, anovulation, tubal blockage, endometriosis, polycystic ovary syndrome and uterine abnormalities are among potential issues for women. In male-factor infertility, there may be issues in sperm count, motility, morphology, volume, pH and other factors. As a result, the overall population of infertile couples is highly fragmented. While there are millions of infertile couples, the specific population eligible for any individual study may be small. Thus, planning for each infertility trial must begin with a meticulous review of the protocol to determine as precisely as possible just how many couples will be eligible. Health Decisions and our therapeutic advisors and clinical staff, as well as the KOLs and PIs in our site network, understand the challenges of planning infertility studies, recruiting eligible subjects and executing such studies with high efficiency and quality.