Yours is, in fact, a good question. The exact answer for your query lies in understanding the phrase " in addition to " used in section 10 of the MB Act,1961. Normally, the phrase " in addition to" refers to "some thing extra which would be available after some thing else already in existence". Therefore, whatever mentioned as "in addition to" is an extra which becomes later in chronological sequence.
Coming to the maternity benefit contemplated under the Act, simply put, it is the leave of absence with wages and continuity of service. If you scan sections 5(1), 9 and 9-A of the Act, you will find that the central points of reference are the " day of delivery", "medical termination of pregnancy", "miscarriage"and "tubectomy operation"respectively. Therefore, the additional leave of one month u/s 10 can be availed of only after happening of such incidents.
The leave of absence due to other sickness is covered under the pre-natal portion of the maternity leave.
1st September 2019 From India, Salem