Premature infants have >10 IQ points drop, and as hospitals reduce their threshold of viability to 24 or 23 weeks, these infants often have really significant cognitive defects. Here in NZ around 1/3 of these infants will fail the end of year exams at age 15, vs 10% of the non-premature population. Fortunately this isn't "negative eugenics" it isn't a change in genes which cause this.