Vaping (E-cigarettes)

Pregnancy

MotherToBaby's fact sheet says that only a few studies examine vaping during pregnancy, but the Jan 1, 2026 reference page lists many studies and Fielder et al.'s 2026 scoping review counted 30 human studies and 34 animal studies. The broader human evidence remains heterogeneous and mostly observational; most studies use self-reported exposure without biochemical confirmation. Deprato et al. (2025) reviewed 23 studies with 924,376 participants, including 7,552 reporting vaping-only use, and reported associations versus non-use for preterm birth (OR 1.49), low birth weight (OR 1.56), and small-for-gestational-age birth (OR 1.48). Vallée et al. (2025) pooled 9 studies with 423,680 pregnant participants and reported higher odds of preterm birth, low birth weight, and small-for-gestational-age birth versus non-smokers. Sukhato et al. (2025), which included 12 studies and excluded overlapping database samples, found higher odds of preterm birth (OR 1.67) and a lower mean birth weight (57 g lower) versus non-use, but no significant difference in small-for-gestational-age birth or miscarriage. Johnstone et al. (2026) included 22 studies from 10 independent samples; it reported higher odds of preterm birth versus non-exposed births, no significant small-for-gestational-age difference, and lower birth weight, with low-to-moderate confidence for comparisons with non-exposed births. Mylavarapu et al. (2026) reported higher odds of low birth weight and small-for-gestational-age birth, but its preterm-birth estimate was not statistically significant; the review noted heterogeneity, publication-bias concerns, self-report, and residual confounding. Fielder et al. (2026) concluded that the literature is too heterogeneous for firm risk conclusions and did not perform a formal risk-of-bias assessment. These reviews use different search windows, comparators, and methods; several include overlapping populations, and they do not establish that vaping caused the outcomes. For miscarriage, MotherToBaby says the evidence is uncertain. Cohn et al.'s PATH cohort (1,037 pregnant participants) found no association between past-month e-cigarette use and adverse pregnancy or birth outcomes, but vaping was rare and the abstract gives no separate birth-defect estimate. Nanninga et al.'s Dutch cross-sectional survey (1,937 participants; 0.5% e-cigarette-only) reported more miscarriages among e-cigarette users than tobacco users, but the small subgroup and comparator do not establish a causal association. Sukhato et al.'s meta-analysis found no significant miscarriage association. The high-stakes claims about birth defects and miscarriage therefore remain uncertain, not established as vaping-caused effects. A single 2025 case report describes a newborn with withdrawal-like symptoms after heavy maternal vaping during pregnancy and lactation; it cannot establish causation. O'Connell et al. (2025) reviewed neurobehavioral development but only one included human study involved e-cigarettes, so it does not establish a vaping-specific human developmental effect. Le et al.'s preconception cohort found no association with spontaneous abortion, but exposure was before pregnancy and the paper was first published online in July 2025, so it does not answer the trimester-specific question.

Breastfeeding

MotherToBaby says nicotine passes into breast milk and advises against e-cigarette use while breastfeeding. Its statement that studies show heart-rate and blood-pressure effects is broader than the primary evidence located: Dahlstrom et al. (2008) studied 38 mother-infant pairs, including 18 mothers who smoked, and found milk nicotine correlated with lower heart-rate variability in boys; infants of smoking mothers had a smaller difference in mean arterial pressure between sleep states. This study involved maternal smoking, not vaping, and does not show that e-cigarette exposure caused harm. CDC says mothers who use e-cigarettes can breastfeed if they cannot quit and that breast milk remains the recommended food for an infant. The Academy of Breastfeeding Medicine reports that no safety data exist for vaping during breastfeeding and recommends first-line cessation treatments for breastfeeding mothers. LactMed's record concerns nicotine; it summarizes the single reported newborn with elevated cotinine and withdrawal-like symptoms after maternal vaping during pregnancy and lactation, and considers nicotine replacement products compatible based on clinical needs. Nicotine replacement compatibility does not establish compatibility of vaping or its full aerosol. The direct human evidence about e-cigarette exposure through milk located here consists of a single case report; that report cannot establish cause.

What was tested

Pregnancy evidence includes cross-sectional surveys, cohorts, population surveillance studies, and systematic reviews of observational data. E-cigarette exposure is often self-reported, vaping-only groups are small, some studies include dual use, and study definitions and comparison groups differ. Human research rarely measures device, nicotine concentration, frequency, or exposure by trimester. Animal and laboratory studies examine mechanisms but do not establish human pregnancy outcomes. The randomized trials reviewed tested smoking cessation, not fetal effects of vaping. A 2026 network meta-analysis of 11 cessation trials found improved point-prevalence abstinence for e-cigarette interventions versus usual care (RR 1.81, 95% CI 1.11 to 2.93), but this is evidence about quitting cigarettes, not evidence that vaping is compatible with pregnancy; the trial evidence was limited and several studies had risk-of-bias concerns. O'Connell et al. found only one human e-cigarette study in a 2025 neurobehavioral meta-analysis. Breastfeeding evidence directly about vaping consists of case-level evidence; nicotine-transfer and infant heart-rate studies mostly concern cigarette smoking or nicotine replacement.