How much caffeine is safe during pregnancy? New review finds no clear threshold

By Hugo Francisco de SouzaReviewed by Laura ThomsonOct 10 2025

While moderate caffeine may spare mothers major complications, new research warns even small doses can subtly stunt fetal growth, and no truly ‘safe’ threshold has been confirmed.

In a recent narrative review published in Nutrients, researchers collated and synthesized decades of research to interpret the clinical impacts of maternal caffeine consumption on pregnancy and fetal outcomes. Study outcomes revealed that while human outcomes are less severe than those observed in animal models (growth restriction and organ malformations), maternal caffeine consumption is nuanced and should be met with careful counselling.

Specifically, the review revealed that moderate caffeine intake (under 200 mg/day, though definitions vary across studies) is generally not associated with major complications such as gestational diabetes, gestational hypertension, or preeclampsia, although evidence remains inconsistent across studies. Importantly, even at these levels, some studies report associations rather than proven causal links with reduced birth weight, highlighting a dose-dependent risk and suggesting possible negative implications of caffeine consumption during the critical gestation period.

Caffeine and pregnancy

Caffeine, the active ingredient of several of the world's most popular beverages, including tea and coffee, is witnessing unprecedented global popularity. This is fueled by a growing body of evidence highlighting its physiological and sports-performance-enhancing properties.

Recent reports now estimate that up to 85% of all adults consume caffeine daily, with pregnant women being no exception. Unfortunately, despite its validated benefits and relatively robust physiological safety profile, mechanistic investigations, particularly in animal models, suggest that the psychoactive substance can cause significant harm to fetal growth and development.

Critically, recent research has found that a pregnant woman's ability to metabolize caffeine slows dramatically as the pregnancy progresses. The half-life of caffeine (~4 to 5 hours in a non-pregnant adult) can extend up to ~15 hours in late pregnancy, exposing both mother and fetus to the substance for much longer periods than usually anticipated.

Consequently, major health organizations like the American College of Obstetricians and Gynecologists (ACOG) and the World Health Organization (WHO) have established several caffeine safety guidelines, generally recommending pregnant women limit their intake to 200 mg/day (ACOG) or below 300 mg/day (WHO). However, the review emphasizes that no universally accepted "safe" level exists.

Unfortunately, given the severe outcomes observed in animal models (growth restriction and organ malformations), critics argue that even these moderate daily dosages may not be sufficient to prevent subtle, long-term effects on child development, from behavioral changes to metabolic health. The review stresses, however, that such risks remain under investigation and the human data are less definitive.

About the study

The present narrative review aims to leverage up-to-date scientific data to address this knowledge gap, providing prospective mothers and clinicians with the recommendations necessary to ensure a healthy pregnancy and improve offspring's long-term outcomes.

The review integrated two distinct streams of research: preclinical data from animal and in vitro studies, and clinical data from human observational studies and meta-analyses. This dual approach was employed to connect the mechanisms of harm seen in the lab with the real-world risks observed in human populations.

The review focused on research published within the past five years for clinical human studies (with no time limit for preclinical evidence). It examined caffeine's impact on a wide range of measurable outcomes, including major pregnancy complications (like gestational diabetes and preeclampsia), fetal growth, and long-term child health.

Study findings

The review highlights a significant discrepancy between preclinical animal models (mainly mice) and clinical human trials. While the former consistently link prenatal caffeine exposure to a broad range of severe adverse effects (intrauterine growth retardation (IUGR), metabolic problems, DNA damage), recent evidence suggests that outcomes in humans are far more nuanced and substantially less severe.

Current evidence suggests that moderate maternal caffeine intake is not clearly linked to a higher risk of gestational diabetes, gestational hypertension, or preeclampsia. However, these findings must be interpreted cautiously due to study limitations.

However, caffeine consumption and fetal growth did demonstrate a repeated though variable dose-dependent association (high caffeine consumption resulted in lower fetal body weight), suggesting that even with moderate intake (<200 mg daily), caffeine may still be associated with small for gestational age (SGA) cases.

Some observational studies also indicate possible links between higher caffeine intake and increased risk of preterm birth (for example, one study found nearly double the risk, RR = 1.94, 95% CI: 1.12–3.37), though meta-analyses have reported inconsistent results overall.

Emerging data also suggest potential long-term effects on child neurodevelopment, behavior, and metabolic outcomes, but these findings remain preliminary and require more robust confirmation. Additional outcomes discussed in the review include possible associations with maternal anemia, recurrent pregnancy loss, and labor complications, though evidence in these areas is similarly limited and heterogeneous.

No evidence of a completely safe threshold

The present review consolidates the current scientific understanding of caffeine's risks during pregnancy, highlighting that while moderate consumption is unlikely to cause major maternal complications, there remains no validated evidence of a completely "safe" threshold, particularly concerning fetal growth.

While the pronounced toxicity seen in animal studies is not generalizable to humans, the consistent associations between caffeine intake and fetal birth weight suggest that caffeine may exert subtle biological effects on human development.

Given the dramatic slowdown in caffeine metabolism during pregnancy, the review emphasizes the need for careful intake monitoring and individualized counselling rather than assuming that a single daily guideline ensures safety. The authors stop short of prescribing new quantitative limits, instead stressing caution and the importance of minimizing exposure where possible.

The authors also underscore that most evidence comes from observational studies relying on self-reported caffeine intake, which are prone to confounding and misclassification. This limitation means conclusions must be interpreted with care until stronger evidence emerges.

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