First of all, please note that the leave you need cannot be termed as "Maternity Leave." Maternity leave is granted to a female employee who is in an advanced state of pregnancy or has undergone an unfortunate miscarriage, with specific ceilings for each. The leave you require is a normal kind of leave, probably by producing a medical certificate necessitating absence from duty, which is to be treated based on the normal leave rules of your organization. At best, you can get leave with pay to the extent of credit available, followed by leave without pay. Since you are on probation, there is a possibility that your probation may be extended.
I suggest that you convince your management to permit you to be absent for the specified period by providing proper records. If you look at it from the organization's point of view, there will be a loss of productivity, extra expenses (to employ a temporary person during your absence), etc. In my opinion, your organization is definitely empathetic towards you, and this should be appreciated by you by not extending your leave of absence and rejoining duty.