Dear asnanigee
When you say "Can I Join at new place of Posting...." it implies "working" on that day,at least; because although in practice a new joinee does no work on the day of joining; however she is definitely treated as "ON DUTY".
Hence my suggestion is that you avail of the maternity leave benefit in full, without any worry about our job. You are neither being compelled to join, nor you can be compelled to join, the new place of posting immediately. So why the undue rush to join ? In any case the reporting officer will not accept your joining till you complete your maternity leave tenure.
Your job shall be kept safe at the new place of posting, with the remarks, "On maternity leave".
Warm regards.