Rationale of the study: Gestational diabetes mellitus (GDM) is very common and the rate of women suffering from it expected to increase in the next years. It is associated with maternal and fetal morbidity and the risk is correlated to the patient's degree of glucose control which can be achieved through a change in lifestyle or medication. Several studies have demonstrated the effectiveness of mobile apps in improving obstetric outcomes in GDM. In addition, the LUMEN device is a breathing device that produces dietary and exercise recommendations based on CO2 levels and improves metabolic parameters in patients with type 2 diabetes. No work has been done on its effectiveness in treating GDM. Aims of the study: Comparison of metabolic outcomes in women with gestational diabetes, with or without the use of LUMEN app. Design: This will be an open label parallel group 1:1 randomized-controlled trial Methods: the investigators will recruit women diagnosed with GDM. The women will be randomized to the intervention arm that will use the LUMEN device and app or to the control arm that will use a free mobile tracking app. The women will be required to monitor their blood sugar levels daily and to have GDM follow-up in the feto-maternal outpatient clinic, as is customary in GDM. After the birth, the maternal and neonatal outcome will be recorded. Based on past research data, a recruitment of 170 is needed to demonstrate a 16.7% decrease in insulin use to balance diabetes, with α = 0.05 and β = 80.

Objective The aim of the study is to examine the effect of using Lumen on metabolic parameters and anthropometric variables in patients with gestational diabetes mellitus. Aims and hypotheses Primary aim: To evaluate the rate of progression from GDM-A1 to GDM-A2 between the groups.

Secondary aim: To evaluate the efficacy of Lumen on metabolic parameters, obstetric outcomes, and neonatal outcomes. Hypothesis: the investigators expect that using Lumen would reduce the rate of progression from GDM-A1 to GDM- A2. Methods Design This will be an open label parallel group 1:1 randomized-controlled trial. Participants The study will include up to 170 women diagnosed with GDM. GDM will be defined according to current ACOG (The American College of Obstetricians and Gynecologists) guidelines. A positive glucose challenge test at 24-28 weeks' gestation followed by at least two pathological values in oral glucose challenge or one pathological value and at least one additional risk factor for GDM (a first family member diagnosed with type 2 DM, obesity, history of GDM).

Women in both groups it will use a glucometer and will be instructed in the use of the device. Use will include puncture of the fingertip to obtain a drop of blood and use of a suitable probe to obtain a sugar measurement.

Eligibility criteria

Inclusion criteria:

1. Gravidas aged 18-45 years
2. Singleton pregnancy
3. Diagnosed with GDM in current pregnancy
4. First visit to high-risk pregnancy clinic is no late than 32 weeks' gestation
5. Not treated with diabetes-related medications

Exclusion criteria:

Medications:

1. Insulin and medications for glycemic control
2. Antipsychotics
3. Diuretics
4. Corticosteroids
5. Oncologic treatment

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Conditions:

1. Previous diagnosis of diabetes
2. Renal disease
3. Hepatic disease

Personal requirements:

1. Inability to read and understand English
2. Inability to use a smartphone
3. Any issues arise with using the Lumen device and application
4. Aerobic exercise > 3 times per week Recruitment Women with GDM will be recruited via clinical referrals from the feto-maternal outpatient clinic or the feto-maternal unit in Rambam medical center (RMC) Intervention All the participants will be under regular follow-up of the treating obstetrician in the feto-maternal outpatient clinic. After the diagnosis of GDM the patients (of both groups) will be instructed regarding recommended diet and glucose monitoring as accustomed in our department. After randomization to the lumen group, subjects will use the Lumen device and mobile phone application, which will guide them once a day after the night fast regarding their daily diet, sleep, and routines according to their Lumen measurements. Subjects will need Google Fit (Android) or Apple Health Kit (iOS) and will be encouraged to communicate with a study investigator via the app during the entirety of the study to resolve technical questions about the device and data collection. The control group will use the glucose buddy app and will be managed in accordance with the common guidelines for GDM management. Participants of both group will measure their fating blood glucose levels and their postprandial blood glucose levels and record it in their mobile app.

Inclusion Criteria:

1. Gravidas aged 18-45 years
2. Singleton pregnancy
3. Diagnosed with GDM in current pregnancy
4. First visit to high-risk pregnancy clinic is no late than 32 weeks' gestation
5. Not treated with diabetes-related medications

Exclusion Criteria:

-

Medications:

1. Insulin and medications for glycemic control
2. Antipsychotics
3. Diuretics
4. Corticosteroids
5. Oncologic treatment

Conditions:

1. Previous diagnosis of diabetes
2. Renal disease
3. Hepatic disease

Personal requirements:

1. Inability to read and understand English
2. Inability to use a smartphone
3. Any issues arise with using the Lumen device and application
4. Aerobic exercise > 3 times per week