This is a single-blind, randomized, parallel-group, superiority clinical trial. The study aims to determine whether a single intake of 30g of dark chocolate (≥80% cocoa) by pregnant women with a non-reactive fetal non-stress test (NST) increases the conversion rate to a reactive NST within 20 minutes, compared to observation with a sugar-free white chocolate placebo. A total of 190 singleton pregnant women at 36-41 weeks gestation with a non-reactive NST will be recruited at the Hospital General San Felipe, Tegucigalpa, Honduras. Participants will be randomly assigned to either the intervention group (dark chocolate) or the control group (placebo). The primary outcome is the proportion of NSTs that become reactive. Secondary outcomes include changes in specific cardiotocographic parameters, total monitoring time, need for additional tests, and maternal satisfaction.

Background and Rationale:

The fetal non-stress test (NST) is a cornerstone of antepartum fetal surveillance, used to assess fetal well-being by evaluating heart rate accelerations in response to fetal movements. A non-reactive NST, defined by the absence of sufficient accelerations over a 20 to 40-minute period, is a common clinical occurrence. While it can indicate fetal compromise, a significant proportion (up to 50%) are false positives, leading to unnecessary maternal anxiety, prolonged monitoring, costly additional tests (e.g., biophysical profile, contraction stress test), and potentially unwarranted obstetric interventions like induction of labor or cesarean delivery.

Pharmacological agents like methylxanthines (e.g., theophylline) have been used to stimulate fetal activity, but their use is limited by side effects and regulatory considerations. Dark chocolate, rich in theobromine (a methylxanthine) and flavonoids, presents a safe, low-cost, and culturally acceptable alternative. Preliminary studies suggest that maternal consumption of dark chocolate, particularly with high cocoa content (≥70-80%), may stimulate fetal movement and heart rate reactivity, potentially converting a non-reactive NST to a reactive state within minutes. However, existing evidence is heterogeneous, derived from small studies with methodological limitations, and none have been conducted in the Central American population.

This study aims to fill this gap by rigorously evaluating, in a randomized controlled trial setting, whether a single dose of 30g of dark chocolate (≥80% cocoa) is superior to a placebo in converting a non-reactive NST to reactive in pregnant women in Honduras.

Study Objectives:

Primary Objective: To compare the proportion of non-reactive NSTs that convert to reactive within 20 minutes after maternal ingestion of 30g of dark chocolate (≥80% cocoa) versus a placebo control.

Secondary Objectives:

To quantify and compare the change in specific cardiotocographic parameters (number of accelerations, baseline variability) between the groups.

To compare the total time spent in the fetal monitoring unit between the intervention and control groups.

To determine and compare the need for additional fetal surveillance tests or urgent obstetric interventions within 24 hours following the intervention.

To evaluate and compare the incidence of maternal adverse events (e.g., nausea, heartburn, palpitations) within 24 hours.

To assess maternal satisfaction and acceptability of the intervention using a standardized hedonic scale.

Inclusion Criteria:

• Singleton pregnancy between 36+0 and 41+6 weeks of gestation.
• Baseline Non-Stress Test (NST) classified as non-reactive after a standard 20-minute recording (absence of ≥2 accelerations of ≥15 beats per minute lasting ≥15 seconds).
• Intact amniotic membranes and not in active labor (cervical dilation <4 cm, with absent or irregular contractions).
• Ability to provide written, informed consent.
• Literacy: Ability to read and write (to ensure comprehension of the consent form and study materials).
• Access to a telephone or electronic device for the 24-hour safety follow-up contact.

Exclusion Criteria:

1. Pregnancy-related exclusions:

   • Multiple gestation (twins, triplets, etc.).
   • Known major fetal malformation.
   • Diagnosis of severe fetal growth restriction with abnormal umbilical artery Doppler.
   • Premature rupture of membranes.
   • Active vaginal bleeding or placenta previa with hemorrhage.
   • Suspected or confirmed chorioamnionitis.

2. Maternal medical exclusions:

   • Severe preeclampsia, eclampsia, or HELLP syndrome.
   • Uncontrolled severe hypertension.
   • Pregestational diabetes or gestational diabetes requiring insulin or other antihyperglycemic medication.
   • Capillary blood glucose level >140 mg/dL at the time of screening.
   • Maternal fever ≥38°C or maternal tachycardia >120 beats per minute.

3. Interference with test interpretation:

   • Use of sympathomimetic drugs within 12 hours prior to the study intervention.
   • Maternal cardiac arrhythmias.

4. Contraindications to the intervention:

   • Known allergy to cocoa or chocolate.
   • Severe caffeine intolerance.
   • Phenylketonuria.
   • Gastrointestinal conditions that would prevent oral intake (e.g., intractable vomiting, ileus, obstruction).

only pregnant women

all IPD collected throughout the trial

Beginning 3 months and ending 5 years after the publication of results

Masking: Single (Outcomes Assessor)

Who is masked: The obstetrician analyzing the cardiotocographic tracings (outcome assessor) will be blinded to group assignment. Participants and clinical staff administering the intervention will not be blinded.