A small but important correction to the first part of your answer. Confirmation of a probationer cannot be automatic unless there is a specific provision for "deemed confirmation" in the contract of employment or the standing orders. As long as there are no orders in writing by the employer, the employee remains a probationer only.
Once the Maternity Act of 1961 becomes applicable to the establishment, the employment status of the woman employee, whether she is confirmed, on probation, or temporary, does not matter. As rightly observed by other members above, what is required is that she must have worked for 80 days in the preceding 12-month period.