It's called the Quiverfull movement. I heard about it on NPR this morning.
This is an evangelical Protestant movement in the U.S. which advocates large families on Biblical principles. The name comes from part of Psalm 127, which says that numerous children are a blessing, like a full quiver of arrows.
I would say that this notion would have greater applicability in a society with a lower lifespan and a higher infant mortality rate.
I have encountered variations of the notion that birth control is sinful and that pregnancy should be left up to divine providence. Some of these have struck me as anti-sex, although Quiverfull does not seem to have this bent.
One of the Quiverfull women interviewed on NPR advocated a curious form of evangelism: growing Christianity by outbreeding Islam.
For a contrary approach: vasectomies are on the rise in the U.S. during this recession.