Introduction: Pain experienced during labor is considered one of the main determinants of women's subjective experience throughout this physiological process. In parallel, anxiety is understood as an emotional response triggered by the unpredictability of childbirth, the perception of pain, and concerns regarding fetal well-being. In this context, aromatherapy, classified as a Complementary and Integrative Health Practice (CIHP), is based on the therapeutic use of essential oils (EOs), aiming to promote individuals' physical and emotional well-being. Despite growing interest in incorporating such practices into obstetric care, there remains a significant gap in robust scientific evidence regarding the effectiveness and safety of aromatherapy during labor. Objectives: To evaluate the effect of aromatherapy using essential oils of lavender (Lavandula angustifolia Mill.) and lemongrass (Cymbopogon citratus [DC.] Stapf) in reducing pain and anxiety in women during active labor. Method: This is a randomized, controlled, triple-blind, longitudinal, and prospective clinical trial to be conducted at a public maternity hospital in São Paulo. The sample will consist of parturients aged between 18 and 40 years, with full-term pregnancies, no comorbidities, and no contraindications for the use of essential oils. Participants will be randomly assigned to two groups: inhalation via an aromatic necklace containing lavender and lemongrass essential oils (Experimental Group - EG), or inhalation of a placebo substance with no therapeutic potential (Control Group - CG). Validated instruments will be used to assess the primary outcomes: the Visual Analog Scale (VAS) for measuring pain intensity and the State-Trait Anxiety Inventory (STAI) for evaluating anxiety levels during the active phase of labor, defined as a cervical dilation greater than five centimeters and at least two effective contractions within ten minutes. Data will be analyzed using statistical methods, with a significant level of 0.05 and a 95% confidence interval. The analysis will include descriptive, exploratory, and inferential procedures, applying both parametric and non-parametric statistical tests as appropriate. Expected results: It is expected that laboring women exposed to aromatherapy with lavender and lemongrass will report lower pain intensity and reduced anxiety levels compared to the control group. It is believed that the use of aromatherapy during labor may promote the physical and emotional well-being of pregnant women, support the physiological progression of labor, and enhance maternal satisfaction with the therapeutic approach, without the occurrence of adverse events.

Inclusion Criteria:

• Women aged 18 to 40 years, regardless of parity; Term pregnancy (gestational age between 37 weeks and 41 weeks and 6 days), with a single, live fetus in cephalic presentation;
• Active labor, defined as cervical dilation ≥5 cm, confirmed by vaginal examination, and the presence of at least two effective uterine contractions (≥40 seconds) within 10 minutes;
• Pain score ≥4 assessed by the Visual Analog Scale (VAS), and anxiety level ≥30 assessed by the State-Trait Anxiety Inventory - State (STAI-S) at the pre-intervention moment;
• No language barriers that would prevent understanding of the Portuguese language.

Exclusion Criteria:

• Presence of obstetric comorbidities or systemic conditions, such as hypertensive disorders, metabolic disorders, hemorrhagic conditions, pulmonary diseases (e.g., rhinitis, asthma), heart diseases, coagulation disorders, autoimmune diseases, among others;
• Prior use of pharmacological analgesia before the intervention (e.g., epidural analgesia, nitrous oxide, scopolamine butylbromide);
• Prior use of anxiolytics or antidepressants, regardless of pharmacological class;
• Presence of olfactory disorders that may interfere with the administration of essential oils;
• Known allergies to essential oils or hypersensitivity reactions occurring during the study.

Individuals who self-identify as women and are in labor are eligible to participate; eligibility is also based on biological capacity for pregnancy and childbirth.

Individual participant data will not be shared due to privacy and confidentiality concerns, as well as institutional and ethical restrictions.

The study will adopt a triple-blind design, with masking of participants, researchers, and statisticians:

Participants: Will be blinded to the intervention received, as the necklaces and substances (essential oils and placebo) will be sensorially indistinguishable; Research team: Investigators responsible for data collection will be blinded to group allocation; Data analyst: Statistical analysis will be performed using a coded dataset (e.g., Group A and Group B), and group identification will only be revealed after completion of the analyses.

To reduce detection bias, there will be a distinction between researchers administering the intervention (experimental or control) and those assessing outcomes. This separation of roles helps prevent differential behavior based on knowledge of participants' group allocation.