This study is a randomized controlled clinical trial designed to evaluate the effect of a polyphenol-rich dietary intervention during pregnancy on endothelial function, oxidative stress biomarkers, and maternal and neonatal outcomes.

Pregnancy is associated with metabolic and vascular adaptations, and complications such as gestational diabetes and hypertensive disorders are linked to endothelial dysfunction and increased oxidative stress. Dietary factors, particularly adherence to the Mediterranean diet and intake of polyphenol-rich foods, may play a protective role.

Pregnant women will be randomly assigned to either an intervention group or a control group. The intervention consists of daily consumption of 10 g of natural non-alkalized cocoa and structured dietary counseling aimed at achieving at least five daily servings of fruits and vegetables, alongside general Mediterranean diet recommendations.

The intervention will last 12 weeks, from early to mid-pregnancy. Biomarkers of endothelial function and oxidative stress will be measured at different time points, along with clinical maternal outcomes (including gestational diabetes and hypertensive disorders) and neonatal outcomes.

The aim is to determine whether this dietary intervention improves endothelial function, reduces oxidative stress, and contributes to better pregnancy outcomes.

Inclusion Criteria:

• Pregnant women aged 18 years or older.
• Singleton pregnancy.
• Gestational age between 8 and 11 weeks at enrollment.
• Receiving prenatal care within the Salamanca Health Area.
• Able to understand the study information and provide written informed consent.
• No clinical restrictions that would contraindicate dietary modifications.

Exclusion Criteria:

• Medical or obstetric conditions that contraindicate dietary modifications.
• Active metabolic, renal, or hepatic disease.
• Severe hyperemesis gravidarum or gastrointestinal disorders limiting food intake.
• Allergy or intolerance to cocoa.
• Habitual high cocoa or chocolate consumption (>30 g/day).
• Multiple pregnancy.
• Severe obstetric complications diagnosed before enrollment.
• Inability to comply with study procedures, attend follow-up visits, or communication barriers that could interfere with participation.

At present, there is no finalized plan for sharing individual participant data (IPD). Due to the sensitive nature of maternal and neonatal health data and the presence of biological and clinical information, data sharing will be considered in accordance with institutional ethics requirements, participant consent, and applicable data protection regulations.

Any potential future sharing of de-identified data will be determined after study completion and in line with publication and regulatory requirements.

Biological samples will be analyzed by laboratory staff blinded to group allocation. Samples will be coded prior to analysis to ensure that outcome assessors are unaware of whether participants belong to the intervention or control group. This procedure is intended to minimize measurement bias in biochemical and oxidative stress biomarkers.