I am sure you will get reprieve.
Having said , try to put in record when you initiate correspondence with the company as to facts and give notice of 15 days and then arrange legal notice on same lines.
I dont think the Management has any option to deny the maternity benefit legally and as per Maternity Act.
Do not delay.
I appreciate the answer of learned member Mr. Narasimhan but I would suggest you should go for other job option too, because a legal fight with ex. employer will may lead some difficulties while working with them again. You can file a complaint against them and seek help of good lawyer. You don't have proof and court need proof. So think wisely and take decision accordingly. As you said you didn't got salary in the tenure of ML, so you can use this thing in favor of you. Rest seniors can help with more clarity.
You have dug your own grave by submitting resignation during pregnency. I do not see anything good come out of a legal battle rather drag you to problems. But you think to go for a legal fight for justice, the resignation from your job would stand as hurdle. You can discuss the matter with a reputed lawyer and do what would be the best for the issue.
You are desperetely in search of job, then the offer of joining your past employer can be an option if other opportunity is not with you.
It would have been better if you could have sought direction before resigning the job. Mr. Narasimhan TS gave his valid views to fight for justice, but one should have patience to reap the benefit legally sanctioned under Maternity Act. Now you and your spouse to decide how to move in the matter for a good.