By what criteria would the unborn be citizens?
That one of the reasons our Constitution was established was to secure the blessings of liberty to our offspring does not establish the citizenship of the unborn - it gives one of the reasons our government was established.
The unborn do not have to be legally defined as citizens (and they are not) to have rights that should be (but are not) respected under our Constitution.
This has been gone over previously.
Erroneously covered before and again now imho.