Found on one of their fan pages:

Q: Are the Duggars part of the QuiverFull movement?
A: The Duggars write in their second book, A Love That Multiplies: “Even though Wikipedia and some Internet blogs report that we are part of a QuiverFull movement, we are not. We are simply Bible-believing Christians who desire to follow God’s Word and apply it to our lives” (page 92).

I don’t have the book to double check.