Effect of an Early and Intensified Nutritional Intervention on the Risk of Developing Gestational Diabetes Mellitus. (MedDiet in GDM)

Effect of an Early and Intensified Nutritional Intervention Based on a Mediterranean Diet (MedDiet) in Women With Clinical-genetic Risk of Developing Gestational Diabetes Mellitus (GDM): a Randomized, Parallel, Interventional, Controlled Clinical Trial

The goal of this clinical trial is to learn if a nutritional intervention based on a Mediterranean diet, initiated early in pregnancy, reduces the incidence of gestational diabetes mellitus (GDM) and other adverse maternal, fetal and obstetric events in pregnant women considered high-risk. It will also learn about the stratification of GDM risk based on clinical, anthropometric, analytical and genetic characteristics.

The main questions it aims to answer are:

• Does the nutritional intervention based on MedDiet reduce the incidence of GDM in women with high risk?
• How can we stratify the risk of GDM? Researchers will compare an advanced nutritional intervention based on a Mediterranean diet to standard care (general recommendations given at the beginning of pregnancy).

Participants will:

• Receive intensive nutritional counselling or standard regular recommendations during the first trimester of pregnancy.
• Visit the clinic at the time of the first ultrasound (gestational week 8-11) and at the time of screening for GDM (gestational week 24-26).
• Undergo a genetic test performed with a buccal swab.

Study Overview

• Status: Not yet recruiting
• Conditions: Pregnancy; Gestational Diabetes Mellitus (GDM); Mediterranean Diet
• Intervention / Treatment: Other: Nutritional intervention based on a Mediterranean diet

• Study Type: Interventional
• Enrollment (Estimated): 1200
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Ana M. Ramos-Levi, MD., PhD.; Phone Number: +33696938427; Email: ana_ramoslevi@hotmail.com

Study Locations

• Spain
  • Madrid
    • Madrid, Madrid, Spain, 28040
      • Hospital Clinico San Carlos
      • Contact: Ana M. Ramos-Levi, M.D., PhD.; Phone Number: +34696938427; Email: ana_ramoslevi@hotmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Unassisted single pregnancy;
• Age between 18 and 50 years old;
• Fasting blood glucose <92 mg/dl in the first gestational blood test;
• First trimester ultrasound before the 12th gestational week.

Exclusion Criteria:

• Multiple or assisted pregnancies;
• Any pregestational illness or pregestational treatment that may affect pregnancy;
• Known intolerance/allergy to any component of the nutritional intervention.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: Standard treatment; The nutritional intervention will consist of providing information on healthy lifestyle measures through an 8-minute informational video (accessible via QR code at the consultation room or the permanent link https://www.youtube.com/watch?v=Qgcz5t9B9WI). Routine obstetric follow-up does not involve subsequent monitoring of adherence to these recommendations, beyond the usual follow-up.
Experimental: Advanced treatment; A specific nutritional intervention consisting of a group session that will last approximately one hour, led by a nutritionist from the research team. This session will explain in detail the key aspects of the MedDiet: consumption of >40 ml/day of extra virgin olive oil, 30 g of nuts per day, 3-4 pieces of whole fruit (not juice), homemade stir-fries, 2-3 servings of vegetables and/or salads per day, 2-3 servings per day of low-fat dairy products, whole grains, 2-3 servings of legumes per week, consumption of fish, limiting the consumption of red meat, and avoiding ultra-processed products, sliced bread, soft drinks, juices, fast food, and pre-cooked products. Two telephonic interviews will be scheduled for follow-up around gestational weeks 16 and 20 to provide motivation and assess and reinforce adherence to these recommendations, emphasizing 5 items: consumption of >40 ml/day of extra virgin olive oil, 30 g of nuts per day, 3-4 pieces of whole fruit (not juice), daily vegetables an	Other: Nutritional intervention based on a Mediterranean diet; The nutritional intervention consists of a 1-hour group session led by a nutritionist from the research team. Includes a detailed description of the key aspects of the MedDiet: consumption of >40 ml/day of extra virgin olive oil, 30 g of nuts per day, 3-4 pieces of whole fruit (not juice), homemade stir-fries, 2-3 servings of vegetables and/or salads per day, 2-3 servings per day of low-fat dairy products, whole grains, 2-3 servings of legumes per week, consumption of fish, limiting the consumption of red meat, and avoiding ultra-processed products, sliced bread, soft drinks, juices, fast food, and pre-cooked products. In addition, 2 telephonic interviews for follow-up (gestational weeks 16 and 20) to reinforce adherence and emphasize consumption of >40 ml/day of extra virgin olive oil, 30 g of nuts per day, 3-4 pieces of whole fruit (not juice), daily vegetables and daily physical activity.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of gestational diabetes mellitus	The general objective of this study is to determine whether an advanced nutritional intervention based on Mediterranean diet reduces the incidence of gestational diabetes mellitus and other adverse maternal-fetal obstetric and endocrine-metabolic events in pregnant women considered high-risk based on a risk score derived from the interaction between associated genetic polymorphisms, baseline clinical characteristics, and anthropometric characteristics of pregnant women. The primary outcome is the comparison of the frequency of GDM, according to IADPSG criteria, between the MedDiet intervention group and the standard treatment group in women at high risk according to the calculated risk of developing GDM.	From enrollment (gestational week 8-11) to the time of screening for gestational diabetes mellitus (gestational week 24-26)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Frequency of maternal complications	Frequency of maternal complications between the MedDiet intervention group and the standard treatment group in women at high risk according to the calculated risk of developing GDM. Variables for this outcome include: maternal weight, weight gain; risk score; frequency of maternal complications (hypertension, eclampsia, infections, carbohydrate metabolism disorders - defined as alterations in normal levels of at least one of the following: fasting glucose, HbA1c, C-peptide, insulin, HOMA-IR)	From enrollment (gestational week 8-11) to delivery
Frequency of fetal complications	Comparison of the frequency of fetal complications between the MedDiet intervention group and the standard treatment group in high-risk women, based on the calculated risk of developing gestational diabetes mellitus (GDM). Variables for this outcome include: birth weight, hypoglycemia, potassium abnormalities, calcium abnormalities, polycythemia, admission to the neonatal intensive care unit (NICU).	From enrollment (gestational week 8-11) to delivery and neonatal period
Frequency of obstetric complications	Comparison of the frequency of obstetric complications between the MedDiet intervention group and the standard treatment group in women at high risk of developing GDM. Variables for this outcome include: type of delivery, dystocia, lacerations during delivery, preterm or postterm delivery (gestational week at delivery).	From enrollment (gestational week 8-11) to delivery and immediate postpartum

Collaborators and Investigators

• Sponsor: Hospital San Carlos, Madrid

Study record dates

Study Major Dates

• Study Start (Estimated): September 15, 2026
• Primary Completion (Estimated): October 31, 2028
• Study Completion (Estimated): December 31, 2028

Study Registration Dates

• First Submitted: September 8, 2026
• First Submitted That Met QC Criteria: September 8, 2026
• First Posted (Actual): September 14, 2026

Study Record Updates

• Last Update Posted (Actual): September 14, 2026
• Last Update Submitted That Met QC Criteria: September 8, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: pregnancy; gestational diabetes mellitus; genetic polymorphism; mediterranean diet; poligenic risk score
• Additional Relevant MeSH Terms: Urogenital Diseases; Endocrine System Diseases; Female Urogenital Diseases and Pregnancy Complications; Metabolic Diseases; Pregnancy Complications; Glucose Metabolism Disorders; Diabetes Mellitus; Nutritional and Metabolic Diseases; Diabetes, Gestational
• Other Study ID Numbers: PI25_01413; 25/902-EC_X (Other Identifier: Ethics Committee of the Hospital Clinico San Carlos)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

IPD Plan Description

The original protocols of the study will be stored in a locked office in the Department of Endocrinology at our Hospital. De-identified data will be saved on a secure electronic database. Specifically, we will use REDCap® (Vanderbilt University) software, which is known to be a secure, browser-based web application (http://project-redcap.org), for data entry and analysis.

All participant data related to the study, including scales and questionnaires, will be completed in paper form, and will then be recorded and uploaded in the REDCap®Electronic Data Collection Record (eCRD).

• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No