Long-term Effects of Flash Glucose Monitoring System in Patients With Gestational Diabetes

The purpose of this study is to report the glycemic control effect and clinical safety and effectiveness of mother and fetus when using a continuous glucose monitoring system (CGM) \[Freestyle Libre\] for a long period of time compared to self monitoring blood glucose(SMBG) in gestational diabetes patients.

The investigators plan to conduct a randomized clinical trial among patients with Gestational Diabetes Mellitus (GDM). The intervention group will use Continuous Glucose Monitoring (CGM) throughout the study period, scanning four or more times per day. The control group will be instructed to perform Self-Monitoring Blood Glucose (SMBG), also four or more times per day.

Eligible participants are those within 24 to 30 weeks of gestation (Visit 0). These subjects will undergo a 1-week run-in period, during which they will wear a retrospective CGM device and perform SMBG four or more times daily as a part of the screening process (Visit 1).

Following the run-in period, subjects will be randomly assigned to either the CGM group (using the Freestyle Libre device) or the Control group (using SMBG). Members of the control group will be asked to perform SMBG four or more times daily, while those in the CGM group will be instructed to scan their CGM four or more times per day.

Participants will have clinic visits at intervals ranging from 2 to 4 weeks, the frequency of which will be determined at the discretion of the attending physician (Visits 2, 2', 2'', 2''', 2''').

Upon reaching gestational age 34-35 weeks (Visit 3), members of the control group will begin to wear a retrospective CGM device until they reach gestational age 36 weeks (Visit 4).

After 6-12 weeks from delivery, subjects will be asked to visit the clinic again and undergo a 75g Oral Glucose Tolerance Test (OGTT) (Visit 5).

For the purposes of data analysis and outcome determination, the most recent 1-week CGM data collected at Visit 4 will be used for both groups.

Eligibility Criteria:
\[Inclusion Criteria\]

1. 19-40 aged female
2. Gestational diabetes diagnosed at 24 to 28 weeks of pregnancy screening (stage 1 or stage 2 approach)

   * 2-1.Screening one-step approach (75g oral glucose tolerance test, diagnosed when one or more of the following)

     * Fasting blood glucose 92 mg/dL or higher
     * Blood glucose 180 mg/dL or higher 1 hour after glucose loading
     * Blood glucose of 153 mg/dL or higher 2 hours after glucose loading
   * 2-2. Screening two-step approach (50 g oral glucose tolerance test then,100g oral glucose tolerance test)

     * If the blood glucose level is 140 mg/dL or higher for 1 hour after the 50g oral glucose tolerance test,
     * 100g oral glucose tolerance test 2 or more of the following

       1. Fasting blood glucose 95mg/dL or higher
       2. Blood glucose 180mg/dL or higher 1 hour after glucose loading
       3. Blood glucose of 155 mg/dL or higher 2 hours after glucose loading
       4. Blood glucose of 140 mg/dL or higher 3 hours after glucose loading
3. Singleton Pregnancy

\[Exclusion Criteria\]

- pregestational diabetes (Overt diabetes)

1. Diabetes Before Pregnancy
2. At least one of the following at the first prenatal visit

   * Fasting blood glucose 126mg/dL or higher
   * Random blood glucose 200mg/dL or higher