Hi,
we have recently answered the same question from another user, please look here:
https://a-kasser.dk/qa/848/residency-normal-maternity-benefits-during-unemployment
Because you are on maternity leave as an employed, and you meet the employment requirement stated in the maternity law ("Barselsloven, §27, stk. 1, nr. 1"), your maternity benefits is not depending on A-kasse membership. In this case you will not be affected by the new rule.
Best regards,