Goisis A, et al. - Since children born after medically assisted reproduction are at higher risk of adverse birth outcomes than children conceived naturally, researchers have identified the extent to which this excess risk should be attributed to harmful treatment effects or pre-existing parental characteristics that confound the association. They observed an elevated risk of adverse birth outcomes among children conceived by medically assisted reproduction than did those conceived naturally even after adjustments for the recognized child and parental characteristics (the difference in birthweight of −60 g and 2·15 percentage point increased the risk of preterm delivery).