That's odd, because conservative Evangelicals actually tend to have more kids on average, and have lower divorce rates than the national average.
The evidence is mixed — maybe you’re right on family size (I hope you are) and I’m right on divorce and abortion (I hope that I’m not).
Divorce and abortion rates are high among evangelicals according to recent studies. Widespread marriage breakdown probably means smaller families.
But then I saw a number of articles saying that evangelicals have larger families. So maybe you’re right on that.
http://www.adherents.com/largecom/baptist_divorce.html.