The rate of non-IVF twin births has increased slightly , going from 16 % in 1998 to 19 % in 2011 , according to the study . 77 % of twins , 36 % of triplets , other multiples came from fertility treatments in 1998 . More multiples are the result of the mother taking fertility drugs rather than having IVF . The IVF induced triplet trend peaked in 2011 due in part to new medical guidelines .
77 % of twins , 36 % of triplets , other multiples came from fertility treatments in 1998 . More multiples are the result of the mother taking fertility drugs rather than having IVF . The IVF induced triplet trend peaked in 2011 due in part to new medical guidelines .