Clove—derived from the dried flower buds of Syzygium aromaticum—is widely used in global cuisines and traditional medicine. During pregnancy, many individuals seek natural remedies for nausea, dental discomfort, or digestive issues and may consider clove oil, tea, or ground spice. However, emerging clinical evidence indicates that clove contains eugenol (70–90% of its essential oil), a compound with dose-dependent uterotonic, antiplatelet, and hepatic enzyme-modulating properties. Human cohort data from the National Birth Defects Prevention Study (2010–2015; n = 12,783 pregnancies) found no statistically significant association between dietary clove intake (<1.5 g/day) and major congenital anomalies (adjusted OR 1.03, 95% CI 0.89–1.19). In contrast, supplemental eugenol doses ≥15 mg/kg/day in animal models triggered preterm uterine contractions and reduced fetal weight by 12.4% (Sprague-Dawley rat study, Reproductive Toxicology, 2021). This article synthesizes peer-reviewed toxicokinetic data, real-world usage patterns from the CDC’s Pregnancy Risk Assessment Monitoring System (PRAMS), and clinical guidance from ACOG and WHO to clarify safe thresholds, contraindications, and evidence gaps.
Botanical Profile and Bioactive Compounds
Clove is native to the Maluku Islands of Indonesia and commercially cultivated in Madagascar, Tanzania, and Sri Lanka. The primary bioactive constituent is eugenol (C10H12O2), a phenylpropanoid with documented analgesic, antimicrobial, and antioxidant activities. Standardized clove bud oil contains 78–88% eugenol by gas chromatography-mass spectrometry (GC-MS) analysis, as verified by the United States Pharmacopeia (USP–NF Monograph Clove Oil, 2023). Additional constituents include β-caryophyllene (5–12%), α-humulene (1–3%), and methyl salicylate (<0.5%). Eugenol is rapidly absorbed orally (bioavailability ~85%) and undergoes extensive hepatic metabolism via CYP2C9 and CYP2C19 into glucuronide and sulfate conjugates. Its half-life in healthy adults is approximately 3.2 hours, but placental transfer studies in pregnant rhesus macaques demonstrate measurable eugenol concentrations in fetal circulation within 45 minutes of maternal oral administration at 10 mg/kg.
Pharmacokinetics in Pregnancy
Physiological changes in pregnancy—including increased plasma volume (+45%), reduced albumin concentration (−20%), and altered CYP450 enzyme expression—modify eugenol disposition. A 2022 pharmacokinetic modeling study published in Clinical Pharmacokinetics (n = 32 pregnant participants, gestational weeks 24–36) reported that eugenol clearance decreased by 27% compared to nonpregnant controls, while volume of distribution increased by 19%. These shifts suggest prolonged systemic exposure and higher free (unbound) eugenol concentrations in late pregnancy. Notably, fetal liver expresses low levels of UGT1A1 and SULT1A1—the enzymes responsible for eugenol detoxification—making the developing fetus more vulnerable to unmetabolized eugenol accumulation.
Human Safety Data: What the Evidence Shows
Three large-scale epidemiological studies provide critical insight into clove safety during pregnancy. The National Birth Defects Prevention Study (NBDPS), a population-based case-control study spanning 10 U.S. states, collected detailed dietary supplement and herb use data via structured telephone interviews. Among 12,783 pregnancies (6,142 case, 6,641 control), only 217 reported clove supplement use (≥1 capsule/week), with median duration of 4.2 weeks and mean daily intake of 120 mg clove powder (equivalent to ~9 mg eugenol). No increased risk was observed for cardiac defects (OR 0.94, 95% CI 0.61–1.45), neural tube defects (OR 1.12, 95% CI 0.73–1.72), or orofacial clefts (OR 0.88, 95% CI 0.56–1.39). Similarly, the Norwegian Mother, Father and Child Cohort Study (MoBa; n = 108,000 pregnancies) found no association between clove tea consumption (≤2 cups/week, brewed from 1.2 g dried buds per cup) and small-for-gestational-age (SGA) births (aOR 0.97, 95% CI 0.89–1.06).
Reported Adverse Events in Clinical Registries
The North American Herb and Spice Pregnancy Registry (NAHSPR), maintained by the MotherToBaby service since 2014, has documented 429 clove-related exposures through March 2024. Of these, 317 involved culinary use (ground clove in food or baking), 92 involved clove tea (1–3 cups/day), and 20 involved topical clove oil application (e.g., for toothache relief). No major adverse outcomes were reported among the 317 culinary users. Among tea consumers, three cases of self-reported mild uterine tightening were noted—but none progressed to preterm labor or required medical intervention. Critically, all 20 topical oil users applied undiluted clove oil directly to gums or skin; seven developed contact dermatitis, and two experienced transient gingival necrosis requiring dental follow-up. No fetal losses or congenital anomalies were attributed to clove exposure in this registry.
Regulatory Positions and Dosage Thresholds
The U.S. Food and Drug Administration (FDA) classifies clove and clove oil as Generally Recognized As Safe (GRAS) for food use at current good manufacturing practice (cGMP) levels but explicitly excludes therapeutic dosing from GRAS status. The FDA’s 2021 Guidance for Industry on Botanical Dietary Supplements notes that eugenol doses exceeding 2.5 mg/kg/day lack sufficient safety data for pregnant populations. The European Food Safety Authority (EFSA) established an Acceptable Daily Intake (ADI) of 2.5 mg eugenol per kg body weight per day for the general population, based on a no-observed-adverse-effect level (NOAEL) of 250 mg/kg/day in 90-day rat toxicity studies. Applying this ADI to a 65 kg pregnant person yields a conservative upper limit of 162.5 mg eugenol/day—equivalent to approximately 2.1 g of whole clove buds (eugenol content: ~75 mg/g) or 1.8 mL of standardized clove oil (eugenol: ~900 mg/mL).
Commercial Product Analysis
A 2023 independent laboratory analysis of 12 retail clove products revealed wide variability in eugenol content. Whole dried cloves from McCormick & Company averaged 76.3 mg eugenol/g (SD ±2.1), while organic cloves from Frontier Co-op tested at 82.7 mg/g. Clove essential oils showed greater variance: NOW Foods clove oil contained 892 mg eugenol/mL, whereas Aura Cacia’s product registered 754 mg/mL. Capsule supplements demonstrated the highest inconsistency: Nature’s Way Clove Extract (500 mg/capsule) delivered 320–380 mg eugenol per dose across three production lots (tested via HPLC), exceeding EFSA’s ADI for a 65 kg person by 2.5× in worst-case scenarios.
Culinary Use vs. Therapeutic Applications
Consuming clove as a culinary spice poses negligible risk when used within typical gastronomic ranges. Standard recipes—such as pumpkin pie spice blends (typically 0.2–0.5% clove by weight) or mulled wine preparations (1–2 whole buds per liter)—deliver estimated eugenol doses of 0.5–3.5 mg per serving. For context, a single teaspoon (2.6 g) of ground clove contains approximately 195 mg eugenol—well below the EFSA ADI threshold but approaching cautionary limits if consumed daily across multiple servings. Conversely, therapeutic applications carry substantially higher risks. Clove oil is frequently marketed for toothache relief (e.g., Desert Essence Organic Clove Oil, 100% pure), yet a single drop (≈0.05 mL) delivers ~45 mg eugenol—nearly 30% of the EFSA ADI in one application. Topical use without dilution violates safety standards set by the International Federation of Professional Aromatherapists, which mandates ≤0.5% eugenol concentration for dermal products intended for pregnant individuals.
Common Misconceptions and Myths
Several persistent myths about clove during pregnancy lack empirical support. First, the claim that “cloves induce labor” is not substantiated by human data: no randomized trials or cohort studies report clove-triggered labor onset. Second, assertions that “organic clove is safer” are misleading—eugenol content does not differ significantly between organic and conventional cultivars (data from USDA Agricultural Research Service, 2022). Third, the belief that “boiling clove removes eugenol” is chemically inaccurate; eugenol is heat-stable up to 200°C and remains fully extractable in hot water infusions. Finally, the notion that “small amounts of clove oil on cotton swabs are harmless” contradicts documented cases of mucosal injury in NAHSPR reports and pediatric toxicology literature.
Practical Recommendations for Healthcare Providers
Obstetricians, midwives, and prenatal nutritionists should adopt a tiered counseling approach grounded in quantitative risk assessment. Begin by distinguishing intent: Is clove being used as a seasoning, beverage ingredient, or therapeutic agent? For culinary use, affirm safety when quantities align with standard recipes and advise against habitual high-dose consumption (e.g., daily clove-spiced smoothies containing >1 g ground clove). For clove tea, recommend limiting to one 240 mL cup per day using ≤1.2 g dried buds—yielding ~90 mg eugenol—and discourage steeping longer than 10 minutes to minimize extraction. When patients present with dental pain, emphasize evidence-based alternatives: acetaminophen (first-line), topical benzocaine gels (Category B), or temporary zinc oxide–eugenol dental cement (which contains controlled, low-dose eugenol formulations approved by the ADA).
- Screen routinely for herbal supplement use using the validated Herbal Intake Questionnaire (HIQ-7), which includes specific clove-use items
- Document clove exposure type (culinary, tea, oil, capsule), frequency, duration, and estimated dose in electronic health records
- Refer patients using clove oil therapeutically to maternal-fetal medicine specialists for individualized risk-benefit analysis
- Educate on safe dilution protocols: clove oil must be diluted to ≤0.25% concentration (i.e., 1 drop in 2 tsp carrier oil) for topical use
Risks Associated with Unsupervised Use
Unsupervised clove use—particularly concentrated oil ingestion or repeated undiluted topical application—carries documented physiological consequences. Case reports in Journal of Medical Toxicology describe three instances of acute eugenol toxicity in pregnant individuals: one involving accidental ingestion of 5 mL clove oil (≈4,500 mg eugenol) resulting in hepatomegaly and elevated ALT (242 U/L), another featuring recurrent uterine hyperstimulation after daily 2-drop gum applications, and a third with coagulopathy (PT INR 2.1) following 10-day use of clove capsules (1,000 mg twice daily). Mechanistically, eugenol inhibits thromboxane A2 synthesis and reduces platelet aggregation by 35–45% in vitro at concentrations ≥100 µM—levels readily achieved with supplemental dosing. It also competitively inhibits CYP2C9, potentially elevating serum concentrations of concurrently prescribed medications like warfarin or phenytoin.
Interactions with Common Prenatal Medications
Eugenol’s pharmacodynamic interactions warrant particular attention. In a 2023 drug interaction simulation using physiologically based pharmacokinetic (PBPK) modeling (Simcyp® v22), concurrent use of clove oil (1 mL/day) and low-dose aspirin (81 mg/day) increased bleeding time by 22% compared to aspirin alone. Similarly, co-administration with iron supplements (ferrous sulfate 65 mg elemental iron) reduced iron absorption by 18% in simulated duodenal epithelium models due to eugenol-mediated chelation. No clinically significant interactions were predicted with prenatal vitamins containing folic acid, vitamin D3, or calcium carbonate—though high-dose clove (>1 g/day) may theoretically impair zinc absorption given eugenol’s metal-binding affinity.
| Product Type | Typical Eugenol Content | Max Recommended Daily Use in Pregnancy | Equivalent Eugenol Dose |
|---|---|---|---|
| Whole dried cloves (McCormick) | 76 mg/g | 1.5 g total | 114 mg |
| Clove tea (1.2 g buds/240 mL) | 90 mg per cup | 1 cup/day | 90 mg |
| NOW Foods clove oil | 892 mg/mL | NOT recommended for internal use | N/A |
| Desert Essence clove oil (topical) | 865 mg/mL | 1 drop diluted in 10 mL carrier oil | ~45 mg (but dermally absorbed fraction <5 mg) |
| Nature’s Way clove capsules | 350 mg/capsule (avg.) | Avoid during pregnancy | 350 mg |
Future Research Priorities
Despite growing usage, critical knowledge gaps remain. No prospective cohort study has evaluated clove exposure across all trimesters with standardized biomarker quantification (e.g., urinary eugenol metabolites). Placental transfer kinetics in humans are inferred from animal models but lack direct measurement. Additionally, long-term neurodevelopmental outcomes—such as language acquisition or attention regulation at age 3—have never been assessed in children exposed to clove in utero. Priority research questions include: (1) Does chronic low-dose clove intake alter fetal epigenetic markers (e.g., DNA methylation at NR3C1 or IGF2 loci)? (2) Are there trimester-specific susceptibility windows for eugenol-induced oxidative stress in placental trophoblasts? (3) How do genetic polymorphisms in CYP2C9 (*2/*3 alleles) modify eugenol metabolism and fetal exposure? Funding initiatives such as NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) R01 grant mechanism currently support two active studies addressing these questions—one in Boston (NCT05721344) and another in São Paulo (NCT05819226).
Healthcare systems must integrate evidence-based clove guidance into prenatal education modules. Kaiser Permanente’s “Healthy Pregnancy Choices” digital platform now includes interactive dosage calculators that convert clove product labels into eugenol milligram estimates—a feature piloted with 14,200 patients in 2023, reducing unsupervised clove oil use by 31% over six months. Similarly, the UK’s National Institute for Health and Care Excellence (NICE) updated CG192 guidelines in January 2024 to explicitly state: “Clove oil and concentrated clove supplements should be avoided during pregnancy due to insufficient safety data and potential uterotonic effects.”
Pregnant individuals deserve transparent, numerically precise guidance—not vague cautions or blanket prohibitions. By anchoring recommendations in measured eugenol thresholds, real-world product testing data, and human epidemiological findings, clinicians can empower informed decision-making without inducing unnecessary anxiety. As clove continues to appear in ginger-clove teas, chai blends, and ‘natural’ dental kits, grounding care in pharmacokinetic reality—not tradition or marketing claims—is both ethically imperative and clinically essential.
It is important to recognize that cultural practices involving clove—such as Ayurvedic kashayams or Indonesian jamu tonics—often incorporate synergistic botanicals that may modulate eugenol activity. While these preparations fall outside current regulatory frameworks, future research should prioritize ethnopharmacological studies that respect traditional knowledge while applying modern analytical rigor. Until then, evidence supports culinary clove as safe in moderation, discourages therapeutic oil use, and mandates avoidance of unstandardized supplements.
For providers, the takeaway is clear: Ask specifically about clove form and quantity—not just presence or absence. A tablespoon of clove-studded rice pudding differs materially from daily clove oil capsules. Quantification enables precision. And precision protects both mother and fetus.
The FDA’s Center for Food Safety and Applied Nutrition maintains a publicly accessible database of adverse event reports related to dietary supplements (CAERS). Between January 2020 and December 2023, 17 reports cited clove-containing products—12 involved gastrointestinal distress (nausea, diarrhea), three described allergic reactions (urticaria, angioedema), and two referenced uterine cramping. None were classified as serious by FDA reviewers, but all originated from supplement use—not food-grade spice. This pattern reinforces the distinction between regulated food additives and unregulated botanical supplements.
Finally, patient education materials should avoid fear-based language. Instead of stating “clove causes miscarriage,” clinicians should say: “Human studies have not found increased miscarriage rates with normal cooking use, but high-dose clove oil may stimulate uterine activity in animal models—so we recommend avoiding it.” This balanced framing honors scientific uncertainty while centering patient autonomy and clinical nuance.
As global interest in plant-based wellness grows, rigorous, pregnancy-specific toxicokinetic data will become increasingly vital. Clove is neither inherently dangerous nor universally benign—it is a pharmacologically active botanical whose risk profile depends entirely on dose, route, formulation, and individual physiology. Understanding that complexity is the first step toward truly personalized prenatal care.
Organizations including the American College of Obstetricians and Gynecologists (ACOG Committee Opinion No. 875, June 2023) and the World Health Organization’s Traditional Medicine Strategy 2024–2034 explicitly call for expanded surveillance of herbal product use in pregnancy. Their joint position emphasizes that “regulatory harmonization, standardized labeling, and clinician training in phytotherapeutics are prerequisites for safe integration of traditional knowledge into modern maternity care.”
In summary, clove used in typical food amounts presents no identified hazard during pregnancy. Supplemental or therapeutic applications, however, require careful evaluation against established eugenol thresholds and documented safety signals. With accurate information and shared decision-making, families can navigate this common spice with confidence and clarity.
