From “To Have and To Hold: Reproduction, marriage, and the Constitution,” by Jill Lepore, in the May 25, 2015 New York:
The Constitution never mentions sex, marriage, or reproduction. This is because the political order that the Constitution established was a fraternity of free men who, believing themselves to have been created equal, consented to be governed. Women did not and could not give their consent: they were neither free nor equal. Rule over women lay entirely outside a Lockean social contract in a relationship not of liberty and equality but of confinement and subjugation. As Mary Astell wondered, in 1706, “If all Men are born free, how is it that all Women are born Slaves?”
Essentially, the Constitution is inadequate. it speaks directly only to the sort of people who were enfranchised in 1787; the rest of us are left to make arguments by amendment and, failing that, by indirection.