Would taking maternity leave impact the eligibility of getting the retention bonus?

My company is located in California. Some employees including me were offered the retention bonus as long as I will be actively employed for nine months at a satisfactory performance level. The wording “actively employed” was not cleared defined in the retention bonus letter. After nine months, my employment will be terminated. The retention bonus will be paid in a lump sum on the last day of the nine months. However, I will be on maternity leave starting from the seventh month during the nine month period. Normally the maternity leave would last more than 3 month which means I will be on maternity leave when my employment relationship get terminated. My question is whether on maternity leave would impact the eligibility to obtain the 100% retention bonus on the last day of the nine month period? Will FMLA provide me some protection? I do not think the other employees would not take any PTO during the nine month period. If other employees take paid vacation during the nine month period, I think they would still get the retention bonus on the last day, thus it does not seem to be reasonable if company refuse to provide me 100% retention bonus just because I am on FMLA leave.