"Consent to being born," which I'm going to interpret to mean "consent to being conceived," doesn't make sense since there's no individual to provide consent until the individual exists (after conception). Otherwise, you're entertaining the idea that hypothetical autonomy can trump actions or decisions of real people. It's also purely speculative.

If the argument really is "consent to being born," then that's one arbitrary example among thousands of parents doing something to their offspring that must take place -- as in, is 100% necessary -- for their offspring to survive. In that case, I say consent is implied. If not, once the individual has sufficiently developed, they have ways out any time they choose.