The Ethics of Nicotine Use in Pregnancy, Revisited

The pregnant smoker occupies the most ethically fraught position in the nicotine landscape. Every option available to her—continue smoking, quit with NRT, switch to vaping, use nothing and attempt cold turkey—carries uncertain risks to the developing fetus. The evidence that would resolve these uncertainties doesn't exist, because pregnant women have been systematically excluded from clinical trials of nicotine products for ethical reasons. The result is that the clinician treating a pregnant smoker, and the pregnant smoker herself, must make decisions with life-altering consequences on the basis of incomplete evidence, guided by ethical frameworks that are themselves contested. The science has advanced modestly since this topic was last examined. The ethical tensions have not resolved. They've sharpened.

The evidence on smoking during pregnancy is unambiguous: it's catastrophic for fetal health. Maternal smoking increases the risks of miscarriage, preterm birth, low birth weight, placental abruption, stillbirth, and sudden infant death syndrome. The mechanisms involve both nicotine (vasoconstriction reducing placental blood flow) and the non-nicotine components of cigarette smoke (carbon monoxide reducing fetal oxygen delivery, thousands of toxicants with direct placental toxicity). The absolute risk increases are substantial: smoking during pregnancy roughly doubles the risk of low birth weight and preterm birth, and increases the risk of stillbirth by nearly 50%. There is no safe level of smoking during pregnancy. The goal—eliminating fetal exposure to cigarette smoke—is not controversial. The controversy concerns how to achieve it when the pregnant smoker cannot quit unassisted.

The evidence on NRT during pregnancy is more limited than for any other smoking population, and the gap is structural. Randomized trials of NRT in pregnancy have been small, methodologically challenged (high dropout rates, low adherence), and inconclusive—some showing benefit, some showing no difference from placebo. The safety data is reassuring for short-term use (NRT does not appear to increase the risk of major congenital malformations) but incomplete for long-term outcomes (neurodevelopment, behavior, metabolic health). The pharmacokinetic challenge—pregnancy accelerates nicotine metabolism by roughly 50%, meaning standard NRT doses may be inadequate—is well-documented but rarely addressed in clinical practice. The most defensible clinical position is that NRT during pregnancy is almost certainly safer than continued smoking (because it eliminates the non-nicotine toxicants in cigarette smoke) and may be less safe than complete nicotine abstinence (because nicotine itself has developmental effects). For the pregnant smoker who cannot quit unassisted, NRT represents a harm-reduction intervention—not risk-free, but substantially lower-risk than continued smoking.

The evidence on vaping during pregnancy is essentially nonexistent in the form that clinicians and patients need. No randomized trial has compared vaping to smoking or NRT in pregnant populations. The observational evidence—pregnant women who vape instead of smoke—is limited, confounded, and insufficient to support clinical recommendations. The mechanistic extrapolation from non-pregnant populations suggests that vaping is likely to be less harmful than smoking during pregnancy (because it eliminates combustion products) and more harmful than complete nicotine abstinence (because nicotine exposure persists). The magnitude of the differential—how much safer than smoking, how much riskier than abstinence—is unknown. The clinical conversation about vaping during pregnancy is therefore a conversation about uncertainty: 'We don't have the evidence we need. Here's what the available evidence suggests. Here are the uncertainties. The decision is yours.' This level of uncertainty is uncomfortable for clinicians and terrifying for patients. It's also the only honest communication possible given the state of the evidence.

The ethical framework for decision-making under this kind of uncertainty has been developed in other domains of medicine—the 'harm reduction under uncertainty' principle. The principle holds that when the status quo (continued smoking) is known to be severely harmful, and the alternative (NRT or vaping) is plausibly less harmful based on mechanism and limited evidence, recommending the alternative can be ethically justified even in the absence of definitive evidence. The principle acknowledges the moral weight of uncertainty—recommending something that might cause harm is a grave responsibility—while also acknowledging that inaction is itself a recommendation. Telling a pregnant smoker 'we don't have enough evidence to recommend NRT or vaping' without offering an effective alternative is, functionally, recommending continued smoking. The ethical calculus is not between a risky alternative and a safe status quo. It's between a risky alternative and a catastrophically risky status quo. The lesser of two harms is still harm, but it's also less.

The stigma dimension of smoking during pregnancy complicates the ethical calculus. Pregnant smokers face intense social judgment—from strangers, family, healthcare providers, and themselves. This stigma drives concealment: pregnant smokers are less likely to disclose their smoking honestly, less likely to seek cessation support, and more likely to avoid healthcare settings where they anticipate judgment. The pregnancy smoking stigma is a public health barrier, not just a social problem. Addressing it requires healthcare providers to create environments where pregnant smokers can be honest about their smoking and their struggles with cessation, without fear of judgment or—in jurisdictions that have attempted to criminalize substance use during pregnancy—legal consequences. The ethical framework for nicotine in pregnancy must include not just the risk-benefit calculus for the fetus but the dignity and agency of the pregnant person.

The research gap on nicotine in pregnancy is a self-perpetuating failure. Pregnant women are excluded from research because the research is considered ethically problematic; the research gap means clinicians lack evidence to guide practice; the lack of evidence means pregnant women continue to receive suboptimal care. Breaking this cycle requires recognizing that excluding pregnant women from research is itself an ethical problem—it denies them the evidence-based care that every other population receives. Pragmatic clinical trials that randomize pregnant smokers who have failed conventional cessation to vaping versus NRT versus continued support for abstinence are feasible, ethical (all participants are already exposing their fetuses to cigarette smoke), and urgently needed. The current approach—making decisions with profound consequences on the basis of mechanistic extrapolation and hope—is not ethically neutral. It's a choice to tolerate uncertainty rather than invest in resolving it.