I think there is one bridging phrase to the Declaration of Independence that is in the Constitution, which can be seen as a link to "unalienable rights."
PreambleWe the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, 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.
Note the use of the phrase "Blessings of Liberty." They didn't say "liberty," they said "blessings of liberty." They also capitalized Blessings and Liberty. Why?
In the Declaration of Independence, the Founders said:
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.
Note the use of capitalization for Life, Liberty, and Happiness. Also note that these refer to the rights endowed by the Creator, which would be blessings. By this language, is it possible that Founders meant the Constitution to establish a government that secured the blessing of the unalienable right to Liberty?
Therefore, when they spoke of "securing the Blessings of Liberty to ourselves and our posterity," wouldn't those referred to as "our posterity" be the unborn children who were also "blessed" with the right to Liberty, and the other unalienable rights in the Declaration of Independence?
How can the Founders believe that they were securing Life, Liberty, and the pursuit of Happiness for our unborn future if they were also writing abortion into the Constitution?
-PJ
The Declaration of Independence has no legal authority whatsoever, since it is not part of the Constitution, nor was it passed bu the Congress under the Constitution.