An article in The Atlantic points out something interesting. The abortion rate has been falling dramatically for the last 40 years, after rising sharply in the 1970s (after Roe v. Wade legalized it in 1973).
You might think that this is because of improved access to birth control, but there is almost no evidence to support that view (almost half of all pregnancies in the US are unintended). Or you might think it is because of increased restrictions on abortions, but the decline mainly happened before those restrictions started being enacted in 2010.
The answer is that culturally, single motherhood has largely become acceptable, so more women who become pregnant unintentionally are carrying their babies to term, with or without the father around.
And therein lies the irony. Social conservatives have traded reductions in abortion rates for increases in unwed mothers. Bristol Palin being one notable example.