Continuous Glucose Monitoring Versus Self-Monitoring of Blood Glucose in Women With Gestational Diabetes

Continuous Glucose Monitoring Versus Self-Monitoring of Blood Glucose in Women With Gestational Diabetes: A Pilot Randomized Clinical Trial

Gestational diabetes mellitus (GDM) is a type of diabetes that is first diagnosed during pregnancy. It causes high blood sugar levels and can increase the risk of health problems for both the mother and the baby. Babies may grow larger than expected (macrosomia), which can make delivery more difficult and increase the risk of birth complications. Mothers with GDM are also more likely to need insulin treatment and may have a higher risk of high blood pressure during pregnancy. Good blood sugar control is important to reduce these risks.

The usual way to monitor blood sugar in women with GDM is by self-monitoring of blood glucose (SMBG). This involves pricking the finger several times a day to measure blood sugar levels. Although this method provides useful information, it only shows glucose levels at specific moments and may miss changes that happen during the night or between measurements.

Continuous glucose monitoring (CGM) is a newer method that uses a small sensor placed under the skin to measure glucose levels throughout the day and night. It provides more detailed information about blood sugar patterns and does not require frequent finger pricks. CGM has been shown to improve blood sugar control in people with type 1 and type 2 diabetes, but its benefits in women with gestational diabetes are not yet fully known.

The purpose of this study is to compare continuous glucose monitoring (CGM) with standard finger-prick monitoring (SMBG) in pregnant women diagnosed with gestational diabetes between 24 and 28 weeks of pregnancy. The study will evaluate whether CGM is practical to use, whether women are satisfied with it, and whether it may help improve blood sugar control and pregnancy outcomes.

A total of 100 pregnant women with gestational diabetes will take part in this study. Participants will be randomly assigned (like flipping a coin) to one of two groups:

One group will use a continuous glucose monitoring device.

The other group will continue with standard finger-prick blood glucose monitoring.

Both groups will receive the same medical care, including dietary advice, physical activity recommendations, and insulin treatment if needed. Participants will attend regular pregnancy visits every 2 to 3 weeks until delivery, as part of usual care. No extra hospital visits are required because of the study. Women using CGM will receive training on how to use the device.

The researchers will compare blood sugar control, the need for insulin, pregnancy complications, and newborn outcomes such as birth weight and episodes of low blood sugar after birth. The study will also assess how satisfied women are with their glucose monitoring method and how it affects their quality of life.

This is a pilot study, which means its main goal is to determine whether a larger study should be carried out in the future. The results will help researchers understand whether continuous glucose monitoring could improve the care of women with gestational diabetes and their babies.

Study Overview

• Status: Not yet recruiting
• Conditions: Gestational Diabetes Mellitus (GDM)
• Intervention / Treatment: Device: Continuous Glucose Monitoring (FreeStyle Libre 2); Device: Self-Monitoring of Blood Glucose (Capillary Glucose Meter)

Detailed Description

Gestational diabetes mellitus (GDM) is a condition in which high blood glucose levels are first detected during pregnancy. It usually develops in the second or third trimester and affects a significant proportion of pregnant women worldwide. Although blood glucose levels often return to normal after delivery, GDM is associated with important short-term and long-term health risks for both the mother and the child.

In the short term, poorly controlled blood glucose levels during pregnancy increase the risk of excessive fetal growth (macrosomia or large for gestational age), shoulder dystocia, birth trauma, neonatal hypoglycemia, respiratory complications, and admission to the neonatal intensive care unit (NICU). For the mother, GDM increases the likelihood of hypertensive disorders of pregnancy, cesarean delivery, and postpartum complications. In the long term, women with GDM have a higher risk of developing type 2 diabetes and cardiovascular disease, and their children are at increased risk of obesity and metabolic disorders later in life.

Achieving and maintaining optimal glycemic control is therefore a central goal in the management of GDM. Standard treatment includes dietary counseling, physical activity recommendations, and regular monitoring of blood glucose levels. If lifestyle measures are not sufficient to reach glycemic targets, insulin therapy is initiated.

Currently, the standard method for glucose monitoring in women with GDM is self-monitoring of blood glucose (SMBG). This involves capillary finger-prick measurements typically performed four to six times per day (fasting and postprandial values). While SMBG provides important information, it has several limitations. It captures glucose levels only at specific time points and may miss significant fluctuations, including nocturnal hyperglycemia and postprandial excursions. It also relies heavily on patient adherence and accurate recording of results. Incomplete monitoring or reporting errors may affect clinical decision-making. Additionally, frequent finger pricks can be uncomfortable and burdensome.

Continuous glucose monitoring (CGM) offers an alternative approach. CGM systems use a small sensor inserted under the skin to measure interstitial glucose levels continuously throughout the day and night. The device provides real-time glucose readings, trend information, and metrics such as time in range, time above range, time below range, and glucose variability. These metrics offer a more comprehensive view of glycemic control than isolated capillary measurements.

In individuals with type 1 and type 2 diabetes, CGM has been shown to improve glycemic control, increase time in target range, reduce hypoglycemia, and enhance patient satisfaction. In pregnant women with type 1 diabetes, randomized clinical trials have demonstrated that CGM use can improve neonatal outcomes. However, evidence supporting the use of CGM in women with gestational diabetes remains limited and inconclusive. Observational studies suggest that CGM may detect glycemic abnormalities not captured by SMBG and may be associated with improved perinatal outcomes, but well-designed randomized controlled trials in this population are lacking.

This study aims to address this evidence gap.

Study Design

This is a single-center, parallel-group, pilot randomized controlled trial conducted at Hospital Clínic de Barcelona. The study will include pregnant women diagnosed with gestational diabetes between 24 and 28 weeks of gestation.

A total of 100 participants will be enrolled and randomly assigned in a 1:1 ratio to one of two groups:

Continuous Glucose Monitoring (CGM) Group

Self-Monitoring of Blood Glucose (SMBG) Group

Randomization will be computer-generated and implemented through a secure electronic system to ensure allocation concealment. Due to the nature of the intervention, participants cannot be blinded to group assignment; however, outcome assessors will be blinded when feasible.

Intervention

Participants in the CGM group will receive a CE-marked continuous glucose monitoring device (FreeStyle Libre 2). The device will be used according to the manufacturer's approved indications. Women will receive standardized training on sensor placement, device use, interpretation of glucose trends, and troubleshooting. A capillary glucose meter will also be provided for confirmation of values if necessary.

Participants in the SMBG group will continue with standard capillary glucose monitoring according to usual clinical practice, typically including fasting and postprandial measurements. They will receive standardized education on proper technique and documentation.

Both groups will receive identical clinical management, including dietary advice, physical activity recommendations, and insulin therapy initiation if glycemic targets are not achieved. Clinical decisions will follow established local protocols for gestational diabetes management. Follow-up visits will occur every 2 to 3 weeks until delivery, consistent with routine care.

No additional clinical visits beyond standard GDM management are required. Questionnaires assessing patient satisfaction and quality of life will be administered after two weeks of device use and again at delivery.

Objectives

The primary objective of this pilot study is to evaluate feasibility, including recruitment rate, retention rate, adherence to the assigned monitoring strategy, and completeness of collected data. In addition, preliminary efficacy data will be generated to estimate potential clinical benefits and inform the design of a future larger-scale randomized trial.

Secondary objectives include comparison between groups in:

Neonatal outcomes (birth weight, large for gestational age, neonatal hypoglycemia, NICU admission, obstetric trauma, Apgar scores, umbilical artery pH)

Maternal outcomes (need for insulin therapy, gestational age at insulin initiation, HbA1c levels, gestational weight gain, hypertensive disorders of pregnancy, postpartum hemorrhage, infections, and mode of delivery)

Glycemic control parameters (including CGM-derived metrics such as time in range and glucose variability)

Patient-reported outcomes, including treatment satisfaction, usability, and diabetes-related quality of life

Exploratory analyses will examine associations between CGM metrics and neonatal outcomes, as well as patient engagement with remote monitoring platforms.

Statistical Considerations

As a pilot trial, the sample size of 100 participants is designed to assess feasibility and generate preliminary estimates of effect size rather than to definitively demonstrate superiority. Analyses will follow the intention-to-treat principle. Continuous and categorical outcomes will be compared using appropriate statistical tests, and multivariable regression models will be used to adjust for potential confounders. Effect sizes and confidence intervals will be emphasized to inform future research planning.

Ethical and Regulatory Considerations

The study will be conducted in accordance with the Declaration of Helsinki and applicable European and Spanish regulations governing biomedical research and medical devices. The protocol and informed consent documents will be reviewed and approved by an independent Research Ethics Committee prior to study initiation.

Participation is voluntary. Written informed consent will be obtained before any study-specific procedures. Data will be coded and stored securely in compliance with the General Data Protection Regulation (GDPR). No biological samples will be collected as part of this study.

Significance

This pilot randomized clinical trial seeks to determine whether continuous glucose monitoring is feasible, acceptable, and potentially beneficial for women with gestational diabetes. By collecting comprehensive maternal, fetal, neonatal, and patient-reported data from diagnosis through delivery, the study will provide important preliminary evidence regarding the role of CGM in this population.

If results suggest clinical benefit and operational feasibility, the findings will support the development of a larger, adequately powered randomized controlled trial. Ultimately, this research aims to improve glycemic management strategies during pregnancy and enhance health outcomes for both mothers and their babies.

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Spain
  • Barcelona
    • Barcelona, Barcelona, Spain, 08028
      • Hospital Clinic De Barcelona
      • Contact: Federico Migliorelli, MD, PhD; Phone Number: (+34)932275400; Email: fmiguore@clinic.cat
      • Principal Investigator: Federico Migliorelli, MD, PhD
      • Sub-Investigator: Clara Murillo, MD, PhD
      • Sub-Investigator: Irene Vinagre, MD, PhD
      • Sub-Investigator: Daria Roca

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Pregnant women aged ≥18 years
• Singleton pregnancy
• Diagnosis of gestational diabetes mellitus (GDM) according to local two-step protocol (abnormal 50 g glucose challenge test followed by abnormal 100 g oral glucose tolerance test with at least 2 abnormal values)
• Gestational age between 24 and 28 weeks at time of GDM diagnosis
• Access to a compatible smartphone or digital device with internet connection to allow synchronization and remote upload of glucose data (CGM or SMBG)
• Ability and willingness to provide written informed consent

Exclusion Criteria:

• Preexisting type 1 or type 2 diabetes mellitus
• History of bariatric surgery
• Treatment with metformin during pregnancy
• Chronic systemic corticosteroid therapy
• Known contraindications to use of a CGM sensor (e.g., severe dermatologic conditions at insertion site)
• Inability to comply with study procedures or follow-up

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Continuous Glucose Monitoring (CGM); Participants randomized to this arm will use a real-time continuous glucose monitoring system (FreeStyle Libre 2) from randomization (24-28 weeks of gestation) until delivery. The sensor will be placed by trained staff, and participants will receive standardized training on device use and interpretation of glucose trends. Clinical decisions, including dietary adjustments and initiation or titration of insulin therapy, will be based on CGM data according to local gestational diabetes protocols. A capillary glucose meter will be provided for confirmatory measurements if needed. All other aspects of care will follow standard practice.	Device: Continuous Glucose Monitoring (FreeStyle Libre 2); Use of a CE-marked continuous glucose monitoring system (FreeStyle Libre 2) from randomization (24-28 weeks of gestation) until delivery. The sensor measures interstitial glucose continuously and provides real-time glucose values and trend information. Data are reviewed during routine visits or remotely and used to guide clinical management of gestational diabetes, including lifestyle adjustments and insulin initiation or titration when required. A capillary glucose meter may be used to confirm discordant readings.
Active Comparator: Self-Monitoring of Blood Glucose (SMBG); Participants randomized to this arm will perform standard self-monitoring of blood glucose using capillary finger-prick measurements (typically fasting and postprandial values, 4-6 times daily) from randomization until delivery. Participants will receive standardized education on measurement technique and recording. Clinical decisions, including dietary adjustments and insulin initiation or titration, will be based on SMBG values according to local gestational diabetes protocols. All other aspects of care, including obstetric follow-up, will follow standard clinical practice.	Device: Self-Monitoring of Blood Glucose (Capillary Glucose Meter); Standard capillary self-monitoring of blood glucose using a CE-marked glucose meter from randomization until delivery. Participants perform fasting and postprandial finger-prick measurements (typically 4-6 times daily). Glucose values are reviewed during routine visits or remotely and used to guide clinical management of gestational diabetes, including dietary adjustments and insulin initiation or titration according to local protocols.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Feasibility of Continuous Glucose Monitoring Compared With Standard Self-Monitoring - Recruitment rate	Number of enrolled participants over number of eligible participants	From randomization (24-28 weeks of gestation) until delivery
Feasibility of Continuous Glucose Monitoring Compared With Standard Self-Monitoring - Retention rate	Number of participants completing the study over number of randomized participants	From randomization (24-28 weeks of gestation) until delivery
Feasibility of Continuous Glucose Monitoring Compared With Standard Self-Monitoring - Adherence to assigned monitoring strategy	Proportion of expected glucose readings completed; ≥80% considered high adherence	From randomization (24-28 weeks of gestation) until delivery
Feasibility of Continuous Glucose Monitoring Compared With Standard Self-Monitoring - Data completeness	Percentage of missing key variables	From randomization (24-28 weeks of gestation) until delivery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Neonatal Outcomes - Birth weight	Birth weight, measured in grams	At delivery
Neonatal Outcomes - Large for gestational age	Birth weight over the 90th centile for gestational age	At delivery
Neonatal Outcomes - Neonatal hypoglycemia	Episodes of hypoglycemia requiring treatment	From delivery up to hospital discharge
Neonatal Outcomes - Admission to neonatal intensive care unit	Admission to neonatal intensive care unit	From delivery up to hospital discharge
Neonatal Outcomes - Obstetric trauma	Presence of any neonatal lesion secondary to delivery (e.g., shoulder dystocia, birth injury)	From delivery up to hospital discharge
Neonatal Outcomes - Apgar score	Apgar score at 1 and 5 minutes	At delivery
Neonatal Outcomes - Umbilical artery pH	Umbilical artery pH	At delivery
Maternal Glycemic Control	HbA1c levels	At diagnosis, third trimester, before delivery, postpartum
Maternal Glycemic Control	Time in range (63-140 mg/dL) - CGM group	At diagnosis, every two weeks, before delivery and at delivery
Maternal Glycemic Control	Time above range (>140 mg/dL) - CGM group	At diagnosis, every two weeks, before delivery and at delivery
Maternal Glycemic Control	Time below range (<63 mg/dL) - CGM group	At diagnosis, every two weeks, before delivery and at delivery
Maternal Glycemic Control	Number of abnormal capillary readings - SMBG group	At diagnosis, every two weeks, before delivery and at delivery
Maternal Glycemic Control	Mean fasting and postprandial glucose values	At diagnosis, every two weeks, before delivery and at delivery
Maternal Glycemic Control	Gestational age at first abnormal glucose reading	Third trimester of pregnancy
Insulin Therapy	Need of insulin initiation	From randomization until delivery
Insulin Therapy	Gestational age at insulin initiation	From randomization until delivery
Insulin Therapy	Initial and final insulin dose before delivery	From randomization until delivery
Maternal Clinical Outcomes	Weight before pregnancy, in kilograms	At beginning of pregnancy
Maternal Clinical Outcomes	Weight before delivery, in kilograms	Last visit before delivery
Maternal Clinical Outcomes	Height, in centimeters	Last visit before delivery
Maternal Clinical Outcomes	Mode of delivery (vaginal, instrumental, cesarean)	At delivery
Maternal Clinical Outcomes	Hypertensive disorders of pregnancy (gestational hypertension, preeclampsia, eclampsia, HELLP syndrome)	From randomization until postpartum hospitalization
Maternal Clinical Outcomes	Postpartum hemorrhage	At delivery and postpartum hospitalization
Maternal Clinical Outcomes	Peripartum infection requiring antibiotics	At delivery and postpartum hospitalization
Patient-Reported Outcomes	Treatment satisfaction (Diabetes Treatment Satisfaction Questionnaire, DTSQ)	2 weeks after device initiation and at delivery
Patient-Reported Outcomes	Device usability and acceptance (Glucose Monitoring Satisfaction Survey, GMSS)	2 weeks after device initiation and at delivery
Patient-Reported Outcomes	Quality of life (GDMQ-36 questionnaire)	2 weeks after device initiation and at delivery

Collaborators and Investigators

• Sponsor: Hospital Clinic of Barcelona
• Collaborators: Fundación Sociedad Española de Diabetes
• Investigators: Principal Investigator: Federico Migliorelli, MD, PhD, Hospital Clinic of Barcelona

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): January 31, 2027
• Study Completion (Estimated): May 31, 2027

Study Registration Dates

• First Submitted: February 23, 2026
• First Submitted That Met QC Criteria: April 23, 2026
• First Posted (Actual): April 30, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 12, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Continuous Glucose Monitoring; Patient-Reported Outcomes; Self-Monitoring of Blood Glucose; Glycemic Control; Gestational Diabetes Mellitus
• 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; Investigative Techniques; Therapeutics; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Blood Chemical Analysis; Clinical Chemistry Tests; Diagnostic Techniques, Endocrine; Monitoring, Physiologic; Self-Testing; Self Care; Continuous Glucose Monitoring; Blood Glucose Self-Monitoring
• Other Study ID Numbers: HCB/2025/1154

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: IPD will not be shared due to the sensitive maternal-neonatal data collected and the small sample size, which may pose a risk of re-identification. Data will be handled in compliance with GDPR.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No