Wrong.
Abortion was not part of the platform or agenda for either the GOP or the Democrats in the 1940s. Only the Communists and Socialists advocated openly for it at that time.
Country club Republicans like Rockefeller and Ford would back it later, but it was not a visible issue for the GOP in 1948 or earlier.
And, of course, there is no such thing as a "woman's right to choose."
There is currently a judicially legislated license for murder in the US, however.