It is 80 days, Ashutosh. Now, coming to the legality of termination, you can defend the termination only if the termination letter states the reason for termination. That is, when the appointment order says that "during probation your services shall be terminated 'without assigning any reason' and without notice," then what should be checked is whether they have given the letter of termination with the reason for termination, i.e., poor performance. In such cases only, you have the right to ask for evaluation and relevant papers. On the other hand, if the termination letter simply states that "following clause...of your contract of employment with us, your services stand terminated with effect from..." then you have no other way because the termination is without any reason, and that is permissible during the probation period. When you give a reason, naturally, the employer should have conducted an inquiry, and the reasons should be known to you in advance. You should be given opportunities to defend the charges (of poor performance) etc.
Now, practical issues: If you view from the HR side, will it be congenial to take employment and after a few months take long leave on the ground of sickness or maternity reasons? I don't think yes. If you have more than 4 years of experience, be confident to get another job after your delivery and when you feel yourself to be okay to take up employment elsewhere.
Regards,
Madhu.T.K