Hello Asha
How is your health condition, are you regular in your office. I am not aware unless an employee gives enough reason, any company would force/coax a person to leave. It seems they are giving you some break/sabbatical, from your query one can't find why they are taking such decision.
As per rule, an employee can not be terminated during pregnency and is liable to allow maternity leave with pay.
You need to first read the company handbook and the contract/appointment letter you have signed. Are you in full time/part time/temporary employment/probation/contract or a confirmed employee.
Please donot get distressed, get to the root cause and work it out with your HR people and supervisor since all such matters must be handled amicably to ensure good reputation at both ends paving the way for long term relationship
Good luck
Runa