Pregnancy in Frankfurt - About medical insurances and cost

German statutory health insurance is compulsory for anyone residing in Germany - and none of them (either in the private or public scheme) has such limitations on pregnancy ad child birth medical expenses.
I assume you are talking about international expat insurances - they often have such clauses, but do not fulfil German requirements anyway, so are not applicable in your case (i.e. don't waste your money on any of them!).
Since the statutory insurance regulations are very complicated, I suggest you contact a German insurer to find out if you have to join the public scheme, or the private scheme, or have a choice of either. This depends on many factors, incl. what you will do in Germany, how much you earn and how you were insured before in your home country.

Edited to add: I have never heard of anybody paying for child birth from one's own pocket in Germany, but I suspect it would be prohibitively expensive (especially if there are complications).