If you were covered under the ESI Act, you should have obtained the necessary certification before starting your maternity leave from your authorized ESI Dispensary. At this point, you can consult the Insurance Medical Officer at your ESI Dispensary and the Branch Manager of the relevant ESIC Branch Office to which you are attached. Discuss the matter with them.
I hope that based on your eligibility as per records and the certificate from the private hospital where you received treatment during maternity leave, the aforementioned offices will provide guidance in accordance with the rules and regulations at this stage.
Regards