Certain factors may include any of the following: Time, Budget, Contingency Plans, and any inspection dates.

For time, the PM needs to readjust the gantt chart in order to make up for lost time because of missing a milestone. He has to consider the importance of certain characteristics during development and allocate time to focus on those requirements. When a milestone is missed, priority for certain aspects have to be re-evaluated.

For budget, the PM may have to consider scrapping certain goals on the gantt chart because the budget might be too tight. Other milestones may be axed if the budget is very constricted by the company.

Contingency Plans are necessary if the company is niether will to risk time nor budget during the development of the project. Therefore, the PM may have implemented a contingency plan within the gantt chart where issues like this can be resolved. This proactive mode of thinking of assuming the possibility of failure can save time and budget for the project.

Since this is an FDA approved device that will act in vivo, inspections will be required. So, on the gantt chart, there may be certain milestones that have to be reached before the product can be ready for inspection, so the PM has to be mindful of that.