Plain English Summary
Background and study aims
Gestational Diabetes Mellitus (GDM) is a heath condition that occurs during pregnancy where the body becomes unable to produce enough insulin – a hormone that helps to control the amount of sugar in the blood – to meet the extra needs during pregnancy. The condition usually resolves itself after the mother has given birth. There is growing interest in GDM due to an increase in the number of women being diagnosed with the condition. It can have harmful consequences for both mother and baby. The mother, for example, can develop gestational hypertension (high blood pressure) and pre-eclampsia (a condition that causes high blood pressure and can lead to some serious pregnancy complications if left untreated). GDM can also the baby to grow larger than usual (macrosomia) , which can result in a difficult delivery and the need for induced labour or caesarean section, low blood sugar levels (hypoglycemia), high insulin levels (hyperinsulinemia) shoulder dystocia (a condition where it is difficult to deliver the shoulders of the baby after the head has already been delivered), and an increased risk of obesity (being very overweight) and type 2 diabetes later in life. A significant number of women who have had GDM will develop type 2 diabetes later in life and may be at increased risk of cardiovascular (for example heart) disease. Researchers have looked at the effect of the Mediterranean diet on the prevention of GDM, providing free olive oil and nuts to patients (study record ISRCTN84389045). There is some preliminary data showing a decrease in the number of women developing GDM after eating a Mediterranean diet(with recommendations of reducing fat intake to < 30% and saturated fat < 10% of total intake). This study is looking at whether an universal nutritional recommendation based on the Mediterranean diet in the real clinical setting (for example, a hospital) , with the usual obstetric and endocrinological follow-up will be as effective as when tested as part of a clinical study.
Who can participate?
Pregnant women over the age of 18 with high blood glucose levels.
What does the study involve?
All participants are given advise on diet to be followed during their pregnancy. Recommendations include having fresh vegetables at both lunch and dinner every day and up to 3 pieces of fresh fruit every day. They are also advised to use extra olive oil for cooking and salad dressings, to have nuts every day and to eat 3 portions of semi-skimmed dairy products. They are also told to eat wholegrain cereals and to avoid biscuits, pastries and cakes. They are encouraged to partake of moderate physical activity (for example, to climb four floors of steps four times a day) every day. They are assessed during their usual visits to the Obstetrics department. During their first visit, they are asked to fill in a nutritional questionnaire and give blood samples as well as sit a medical interview. They then receive nutritional recommendations during their second visit and are tested throughout their pregnancy for GDM and to check whether they are following the dietary advice.
What are the possible benefits and risks of participating?
All the participants will gain nutritional education beneficial for the development of their pregnancy. There are no side effects.
Where is the study run from?
Hospital Clínico San Carlos, Madrid (Spain)
When is the study starting and how long is it expected to run for?
February 2016 to November 2017
Who is funding the study?
Investigator initiated and funded
Who is the main contact?
Dr Nuria García de la Torre Lobo
Dr Nuria García de la Torre Lobo
Servicio de Endocrinología y Nutrición.
Hospital Clínico San Carlos. C/Profesor Martín Lagos s/n.
Efficiency of a dietary intervention based on the Mediterranean diet in the clinical setting in the incidence of gestational diabetes mellitus
The efficacy of a nutritional intervention in the clinical setting based on the mediterranean diet is not inferior to the results obtained from a clinical trial (ISRCTN84389045) in the incidence of gestational diabetes mellitus.
CEIC Hospital Clínico San Carlos, 08/11/2016, ref: 16/442-E
Unicentric prospective and interventional
Primary study design
Secondary study design
Non randomised study
Patient information sheet
See additional files
Gestational Diabetes Mellitus
A nutritional intervention based on the Mediterranean diet will be given to all pregnant women attending the study hospital in the first gestational visit (gestational weeks 8 to 12).
All participants will have the usual follow-up visits in the Obstetrics department, and also in the Endocrinology department in case gestational diabetes is diagnosed.
Visit 0: between 8-12 gestational weeks: Consent signature, medical interview, blood sample, and nutritional questionnaire.
Visit 1: one week later: inclusion criteria compliance, blood sample, and nutritional recommendations.
Visit 2: Between 24-28 gestational weeks; oral glucose tolerance test with 75 g of glucose for identification of gestational diabetes with the IADPSG criteria, nutritional questionnaire and blood and urine sample.
Visits 3-4 (and 4’, if needed): Gestational weeks 28 to 38 if they are diagnosed with gestational diabetes for the usual follow up in the Endocrinology department.
Visit 5: 38 gestational week: nutritional questionnaire, blood and urine sample.
Visit 6: 12 weeks postpartum: clinical evaluation, nutritional questionnaire and blood sample.
The intervention will include these main recommendations:
1. To have fresh vegetables at lunch and dinner daily (any type of vegetables)
2. To have fresh fruit for dessert at lunch and dinner daily ( maximum 3 portions a day, avoid juices)
3. To use extra virgin olive oil daily for cooking and dressings
4. To have nuts daily (as snacks and for salads)
5. To have 3 portions of semi skimmed dairies daily
6. To have wholegrain cereals instead of whites. To avoid biscuits, pastries, and cakes
7. To perform moderate physical activity (to climb four floors of steps four times daily)
Primary outcome measure
Incidence of gestational diabetes mellitus at 24-28 gestational weeks. The diagnosis of gestational diabetes mellitus will be established with a 75 g oral glucose tolerance test according to the criteria o IADPSG 2009 and WHO 2013.
Secondary outcome measures
Percentage of women with a weight gain at the last gestational visit (weeks 37-40)
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
Pregnant women older than 18 with fasting glucose levels < 92 mg/dl in the first gestational visit (gestational week 8 to 12).
Target number of participants
Participant exclusion criteria
1. Pregnant women with fasting glucose levels >92 mg/dl in the first gestational visit (gestational week 8 to 12)
2. Intolerance/allergy to nuts or olive oil, multiple pregnancy, and any disease or medical treatment that can have an effect on the intervention. Women with specific nutritional treatments
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Hospital Clínico San Carlos
calle Profesor Martín Lagos s/n
Investigator initiated and funded
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Recruitment will be finished in November 2017. Last patients will give birth in July 2018, so we will publish our data in an original article by the end of 2018.
IPD sharing plan:
Please request access to participant level data by emailing firstname.lastname@example.org
Intention to publish date
Participant level data
Available on request
Basic results (scientific)
- ISRCTN13389832_PIS_26Oct16.doc Uploaded 23/11/2016