Final answer:
A basic fertility workup is typically initiated after a couple has been unable to conceive after one year of regular, unprotected sex. Known factors such as irregular periods or testicular injuries may prompt earlier investigations.
Step-by-step explanation:
A basic fertility workup is often initiated when a couple has been unable to conceive after one year of regular, unprotected sexual intercourse. Infertility is defined as the inability to achieve a successful pregnancy after this period. In cases where there are known risk factors or concerns, such as irregular menstrual cycles or a history of testicular injuries, a workup may be started earlier. From the information provided, since Isabella and Omar have been trying to conceive for a year without success, and given their individual concerns about ovulation regularity and potential sperm issues, initiating a fertility workup would be the appropriate step at this time.