I don't think that the birth, or even the pre-natal care will be much of an issue. First things first, Mexico does have a public healthcare system which co-exists with the private healthcare system. The public one is split into 3 parts, two of which are insurance-based, and require employment in a Mexican company to fully access beyond emergency care, and one of which is free at point of use for anyone, be they nationals, foreigners, tourists, illegal immigrants (which we get plenty of from Central America), it does not matter, it's just free. The private one is more akin to what most Americans will already be used to in the US, you pay up, you can have an insurance plan that allows you to not pay yourself, but it will depend on the particular hospital which insurance plan they take. Now, any and all hospitals, including private ones, are required by law to treat you and not charge you if you have an emergency (some private hospitals will still try to use the public's ignorance on the specific legislation to threaten billing), so the birth and immediate post-natal care would be taken care of, possibly by the Mexican taxpayer, depending on what hospital they pick/have closest to them. The real question comes from the post- and pre-natal care, which, given how I doubt they are insured by private insurance, they'll have to pay out of pocket if they want to go to a private hospital which is much faster and better than an INSABI-afiliated one. There's also been some issues as of the last 4 years (give or take) with medicine stocks for the public healthcare system but they are still not that expensive if they decided to take the public route + buying meds and vaccines from the private sector.
The shitty, grease covered dice are re-rolling on a functional table, at least. If Ralph does basically what anyone would do in the US regarding the birth of a child the new demon should be delivered fine. Still, he can fuck up in completely conventional ways.