OK, the headline is a bit exaggerated, but research being published by London School of Economics political scientist Satoshi Kanazawa in the November 2014 issue of Social Science Research finds in general that the higher a woman's IQ, the lower is her fertility. Here's the abstract:
Demographers debate why people have children in advanced industrial societies where children are net economic costs. From an evolutionary perspective, however, the important question is why some individuals choose not to have children. Recent theoretical developments in evolutionary psychology suggest that more intelligent individuals may be more likely to prefer to remain childless than less intelligent individuals. Analyses of the National Child Development Study show that more intelligent men and women express preference to remain childless early in their reproductive careers, but only more intelligent women (not more intelligent men) are more likely to remain childless by the end of their reproductive careers. Controlling for education and earnings does not at all attenuate the association between childhood general intelligence and lifetime childlessness among women. One-standard-deviation increase in childhood general intelligence (15 IQ points) decreases women's odds of parenthood by 21–25%. Because women have a greater impact on the average intelligence of future generations, the dysgenic fertility among women is predicted to lead to a decline in the average intelligence of the population in advanced industrial nations.
This research prompts me to speculate that the Flynn Effect which finds that average IQs have been rising around the world during the past century likely explains a good bit of the continuing global fall in total fertility rates.
If you'd like to enjoy the column that prompted the most hate email I have gotten so far, see: "Why Are People Having Fewer Kids?: Perhaps It's Because They Don't Like Them Very Much."
Disclosure: My wife and I are childless. And yes, notwithstanding the fact that she married me, she is very, very smart. And as I have earlier disclosed: My wife and I try not to flaunt our voluntarily childless lifestyle too much.