Carbohydrate-Optimized Nutritional Solution Versus Electrolyte Hydration in Labor

Background Pregnancy involves an increase in anabolic metabolism, especially during the third trimester due to continuous fetal and placental growth. During active labor, metabolic demands increase further, reaching levels comparable to moderate or intense physical exercise. A 10-hour labor with epidural analgesia may not be adequately supported by clear liquids, saline, or glucose alone; nutritional support should be better adapted to the energy needs of laboring women.

Recent studies have shown mixed results regarding carbohydrate intake during labor, without a consistent effect on labor duration or mode of delivery, although some evidence suggests benefits for maternal comfort and neonatal glycemia

. A 2016 meta-analysis involving 691 women found that oral carbohydrate supplements in small amounts (mean difference of 195 kcal) did not significantly alter labor duration, cesarean rates, or instrumental delivery rates. A large multicenter trial with 3,984 women found no differences in instrumental delivery rates between carbohydrate and fasting groups.

However, a Chinese multicenter trial involving 1,953 primigravid women with epidural analgesia reported reduced maternal hunger and lower neonatal hypoglycemia with carbohydrate supplementation, although higher rates of maternal and neonatal hyperglycemia were observed.

Aspiration Concerns and Modern Practice Historical restrictions on oral intake during labor stem from Mendelson's 1946 description of aspiration risk during general anesthesia. However, modern obstetric anesthesia has evolved considerably, with neuraxial techniques now standard and general anesthesia rarely used for childbirth. Current guidelines from the American College of Obstetricians and Gynecologists (ACOG) and the American Society of Anesthesiologists (ASA) recommend a moderate intake of clear liquids during an uncomplicated labor, while solid foods are generally avoided.The incidence of aspiration in modern obstetric practice is extremely low.

Myometrial Energy Metabolism and Uterine Perfusion From a physiological perspective, the uterus is an extraordinarily active muscle that significantly increases its energy demand during pregnancy and labor.As a myogenic organ, it generates rhythmic contractions without direct nerve stimulation, and its function critically depends on a continuous supply of metabolic substrates. Uterine perfusion illustrates this need: blood flow increases from approximately 45 mL/min in the non-pregnant state to nearly 750 mL/min at the end of gestation.

The causes of delayed labor can be related to the four "P"s: power, passenger, passage, and psyche. Insufficient power can occur when the myometrium is not adequately loaded with glycogen before labor, leading to myometrial dysfunction. Uterine atony, associated with low contractility, causes between 70 and 80% of postpartum hemorrhages, which are estimated to occur in 5-10% of all births.

Glucose as the Primary Myometrial Fuel Glucose is the primary energy source for the myometrium. Glucose concentrations in uterine tissue at the end of pregnancy vastly exceed those in striated muscle. Glycogen stores increase during gestation as a strategic reserve but are rapidly consumed once labor begins. This depletion has been associated with a higher risk of ineffective contractions and uterine dysfunction.

Mitochondria play a central role in this process. Oxytocin increases mitochondrial depolarization, stimulating ATP production and modulating the rhythmicity of contractions.When glucose availability decreases, the myometrium increases its reliance on anaerobic glycolysis, manifesting in an accumulation of lactate and adenosine, which are classic markers of myometrial fatigue. Despite clear physiological evidence highlighting glucose and adequate hydration as critical components for optimal myometrial contractility, restrictive oral intake policies continue to influence modern obstetric care.

To address this clinical discrepancy, this Randomized Clinical Pilot Trial was designed.

Study Design and Methodology This is an experimental, analytical, and triple-blind randomized controlled pilot trial conducted according to CONSORT guidelines. Participants, clinical staff (midwives), and outcome assessors are blinded to group allocation. The study takes place at the Hospital Universitari de Tortosa Verge de la Cinta (HUTVC), Tarragona, Spain.

Group allocation is random and concealed. The hospital pharmacy prepares intervention packages (4 units per participant) and assigns a unique code to each package. The pharmacy maintains a database linking the codes with the intervention type, but does not have access to the identities of the participants. Midwives dispensing the products are unaware of the group allocation. Both interventions were prepared in identical opaque containers with standardized volume, appearance, and labeling.

Interventions and Administration Protocol Intervention Group (High-carbohydrate sports gel): The gel contains a carbohydrate blend designed to promote sustained energy availability.

Control Group (Low-carbohydrate hydrogel): The product contains a lower carbohydrate content. It is modified using a food-grade thickening agent (xanthan gum) to match the viscosity and mouthfeel of the sports gel, ensuring both interventions are indistinguishable.

The first dose is administered 60 minutes after epidural insertion to prevent confounding effects related to the epidural. Subsequent doses are administered every 3 hours during active labor, up to a maximum of 4 doses per participant. Oral water intake is encouraged throughout labor (150-200 mL/hour)

Inclusion criteria

• Pregnancy classified as Normal Pregnancy, Low-Risk Pregnancy, or Medium-Risk Pregnancy according to the "Protocol de seguiment de l'embaràs a Catalunya" and "Protocol de naixement i acompanyament al naixement de Catalunya".
• Use of epidural analgesia during labor.
• Ability to understand Catalan and/or Spanish.
• Term pregnancy (≥37 weeks gestation).
• Cephalic presentation.
• Spontaneous onset of labor, OR induced labor due to prolonged pregnancy or premature rupture of membranes (regardless of duration).
• Prenatal care at ASSIR Terres de l'Ebre with planned delivery at Hospital Universitari Tortosa Verge de la Cinta.
• Signed informed consent prior to labor.

Exclusion criteria

• Gestational diabetes (including diet and exercise controlled).
• Multiple gestation.
• Labor not documented in partograph.
• Informed consent not signed prior to labor.
• Medical indication requiring administration of glucose or glucose-saline intravenous solution during labor (withdrawal criterion).