IQ is negatively correlated with fertility in most parts of the world, the only exception being Scandinavia to my knowledge. Within the US it also differs among races, with the fertility-IQ correlation being worst among hispanics and blacks, less among whites. Note this is based on polygenic scores, not IQ tests

A result of this is that the black-white genetic IQ gap is widening over time. The genetic component of that 17 point gap is like about 13-14 already and its widening about a point a generation at this rate.