 More generally, the conservative approach to doing research with and treating women during pregnancy emphasizes the risks to fetuses from intervening, but not the risks from not intervening (Lyerly, Little, and Faden 2008b). When we exclude pregnant women from research or discourage treatment because of a lack of knowledge about the effects of a medication, we are not typically erring on the side of fetal safety; rather, we generally have no idea whether it is riskier for the fetus to be exposed to a medication or to the effects of untreated maternal morbidity. As Lyerly, Little and Faden point out, “If research is important to tell us when medications are unsafe, it is also important to reassure us when drugs are safe … In the absence of information about the safety and efficacy of medications, pregnant women and their providers are left with two unsavory options—take a drug, with unknown safety and efficacy; or fail to treat the conditions, thus leaving the woman and fetus vulnerable to the consequences of the underlying medical problems” (Lyerly, Little and Faden 2008b, 12, 19). Pregnant women who have medical needs during pregnancy are typically told to weigh the risks and benefits when deciding whether to proceed with a treatment whose impact on fetuses is unknown. But this is an impossible demand; no one can weigh unknown risks and benefits. Excluding pregnant women from research sustains the impossibility of this calculation, and erring on the side of nontreatment may or may not best protect fetal well-being.