My copy of Guinness Book of World Records is rather old, but it tells me that a Russian mother in the 1700's is verified to have had 69 children. Twenty-seven "confinements", with 16 pairs of twins, 7 sets of triplets, and 4 sets of quads. At least 67 survived infancy.
Also a woman in Argentina (1980's) had produced 32 children who survived.
But the Duggar's are amazing.