As use of the stimulant medications methylphenidate and amphetamines to treat attention-deficit/hyperactivity disorder has increased in the general population,1,2 exposure to these medications during pregnancy has also increased in recent years.3,4 Like many prescription medications, little is known about the effects of stimulant medications on pregnancy outcomes and fetal outcomes.5 Studying prescription medications in pregnancy can be challenging, both because the exposures in a single population may be relatively uncommon and many of the fetal outcomes, particularly specific congenital malformations, rarely happen. Thus, innovative approaches to assessing the risks of prescription medications during pregnancy are necessary to provide information to clinicians who prescribe and women who might take these medications.