If this were the case why do they consistently vote against government support birth control, pregnancy support programs, maternity leave, and aid programs to mothers?

My guess would be because they don't want to spend money on other people, or at least other people that are not inside of "their" group.

That and the inefficiency (in their minds) of government programs and how their hard-earned tax money is spent.

Finally as far as maternity leave goes, they don't want to pay workers and not get work out of them, though I'm not sure that's a conservative only philosophy, or more like a Capitalism one.