I don't see there is a problem with an insurance company offering whatever coverage it chooses to offer as long as the purchaser understand what they are purchasing.
Exactly. And that is where government does have an appropriate policy regulatory role. There are insurance schemes, there is ambiguity, there is predatory selling tactics, there is built-in gotchas, there is deception .... this all occurs throughout our country's business community, this has been the case since the 1800's. That's why Teddy Roosevelt worked so hard t pass the Sherman Anti-Trust Act, which passed, and is the law of our land. It applies to all companies operating on an interstate basis which places them under federal regulatory review, EXCEPT the massive insurance industry, which was EXEMPTED from the Sherman Anti-Trust Act in 1945 when regulated by a state.

The Sherman Anti-Trust Act applies to more than monopolies, it applies to anti-competition behavior, collusion, price-fixing, widespread schemes and plots against consumers that become unfair and deceptive trade practices and fraud.

This is why it's so important to repeal the McCarran-Ferguson Act of 1945 as soon as Congress can get it's head out of its donor lists and focus on the primary "principles" of our nation for the people of the United States and our posterity, including "promote the general welfare".

These "principles" are outlined in the Preamble of the US Constitution, to describe the purpose of the government is created. These principles are listed below:

1. to create a more perfect union
2. insure domestic tranquility
3. establish Justice
4. provide for the common defense
5. promote the general welfare
6. secure the blessings of Liberty

Number 5, "promote the general welfare" is where such things as jobs, wages, trade, immigration, education, health, healthcare and health insurance fall. When we promote the general welfare, and do it right, it prevents US from having to provide welfare.

Is an illegal alien with 6 children in our country "promoting the general welfare" of the people of the United States and our posterity? Well no, of course not. It's quite the opposite, they are harming the general welfare of our citizenry and nation. Is illegal immigration unconstitutional? Absolutely. On every front and every level.

So how can maternity benefits or any other benefit be made available to promote illegal unconstitutional activity in our poor beleaguered nation? If it's illegal to be in the United States, then any and everything you do here is illegal including having sex, which obviously includes breeding.

We've had a lot of really stupid people serve on the US Supreme Court and an even larger number who have worked in the US Government who have forsaken their purpose and obligations and forgotten the people of the United States and our posterity.

The Preamble to the Constitution is an introductory, succinct statement of the principles at work in the full text. It is referred to in countless speeches, judicial opinions, and in a song from Schoolhouse Rock. Courts will not interpret the Preamble to confer any rights or powers not granted specifically in the Constitution.

We the people of the United States, in order to form a more perfect union, establish justice, insure domestic tranquility, provide for the common defense, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity, do ordain and establish this Constitution for the United States of America.
https://www.law.cornell.edu/constitution/preamble

So when people want to talk about our "values" and "principles", keep this link and refer to it often. If whatever issue someone is hanging their "principles of this nation" hat on, check the Preamble. If it's not there, it doesn't count and they need to sit down, shut up and wait for orders on one that is there.