The requirement of apportioning the Maternity leave into 50% each before and after delivery has since been amended and it is explained as follows:
"The maximum period for which any woman shall be entitled to maternity benefit shall be 12 (revised to 26 weeks from 01.04.17) weeks in all whether taken before or after childbirth.
However she cannot take more than six weeks before her expected delivery.
Under the MB Amendment Act 2017, this benefit could be availed by women for a period extending up to 8 weeks before the expected delivery date and remaining 18 weeks can be availed post childbirth Prior to the amendment of 1989, a woman employee could not avail of the six weeks’ leave preceding the date of her delivery; she was entitled to only six weeks leave following the day of her delivery. However, by the above amendment, the position has changed.
Now, in case a woman employee does not avail of six weeks’ leave preceding the date of her delivery, she can avail of that leave following her delivery, provided the total leave period, i.e. preceding and following the day of her delivery does not exceed 12 weeks. (now 26 weeks)"
You can bring the amended provision to the notice of management and tell them in clear terms that insisting on 3 months leave before delivery is in violation of the MB Act and that what is specified is the max. period before delivery (ie. 8 weeks) and in actual terms it could be any thing less than that including ZERO.