Table 2.
Evidence Supporting CGM in Terms of Glycemic Efficacy and Perinatal Complications
| Study | Study design | Study population (n) | Insulin regimen | CGM type and duration | Baseline HbA1c (%) (CGM vs. SMBG) | Primary outcomes | Results (CGM vs. SMBG) | |
|---|---|---|---|---|---|---|---|---|
| Feig et al. (2017) [15] | RCT | 325 T1D: Pregnant (215) Planning pregnancy (110) | MDI or insulin pump (46%) | Continuous use of rt-CGM (Guardian REAL-Time or MiniMed Minilink system) | Pregnant participants: 6.5%–10.0% | Difference in change in HbA1c | Adjusted between-group differences: | |
| Planning pregnancy: 7.0%–10.0% | Pregnancy: at 34 weeks’ gestation | HbA1c (%): −0.19 (P=0.02) 6.35% vs. 6.53% | ||||||
| Mean HbA1c: 6.8% vs. 6.9% | Planning pregnancy: at 24 weeks or conception | TIR (%)a: 68 vs. 61 (P=0.003) | ||||||
| LGAb: 53% vs. 69% (P=0.02) | ||||||||
| Neonatal hypoglycemia requiring IV dextrose: 15% vs. 28% (P=0.02) | ||||||||
| NICU care >24 hr: 27% vs. 43% (P=0.015) | ||||||||
| Kristensen et al. (2019) [8] | Observational study | 186 T1D | MDI or insulin pump (29%) | At least 2 weeks of rt-CGM (Dexcom G4, n=92) or is-CGM (FreeStyle Libre 1, n=94) wear | Differences in glycemic status according to the presence of LGAc | LGA vs. No LGA | ||
| TIR (%): | ||||||||
| 1st trimester: 48.2 vs. 51.9 (P=0.07) | ||||||||
| 2nd trimester: 51.8 vs. 57.9 (P<0.001) | ||||||||
| 3rd trimester: 57.6 vs. 62.2 (P=0.04) | ||||||||
| Voormolen et al. (2018) [33] | RCT | 300 adults: T1D (109) T2D (82) GDM (109) who were on insulin therapy | Insulin-based therapy or insulin pump (19%) | 5–7 days of blinded CGM (iPro2) wear every 6 weeks | 6.8% vs. 7.0% | LGAb | Adjusted between-group HR, 1.06 (P<0.001), 31.0% vs. 28.4% | |
| Murphy et al. (2008) [16] | RCT | 70 adults: T1D (46) T2D (25) | Insulin-based therapy or insulin pump | Up to 7 days of rt-CGM wear every 4–6 weeks | 6.1% vs. 6.4% | Difference in change in HbA1c LGAb | HbA1c (%): 5.8 vs. 6.4 (P=0.007) | |
| LGA: OR, 0.36 (P=0.05), 35% vs. 60% | ||||||||
| Majewska et al. (2023) [17] | RCT | 100 GDM | Initially not on insulin therapy | Intermittent use of is-CGM (FreeStyle Libre 1) during the first 4 weeks after GDM diagnosis | FPG (mg/dL): 87 vs. 92 | FPG and PP1 during the first 4 weeks after GDM diagnosis | FPG (mg/dL) 86.7 vs. 85.1 (P=0.437) | |
| PP1 (mg/dL): 186 vs. 181.5 | PP1 (mg/dL): 113.9 vs. 109.5 (P=0.011) | |||||||
| Macrosomiad: OR, 5.62 (95% CI, 1.16–27.2), 4.1% vs. 30% | ||||||||
| Paramasivam et al. (2018) [37] | RCT | 50 GDM | Insulin-based therapy | 6 days of blinded CGM (iPro 2 Enlite) wear in weeks 28, 32, and 36 weeks of gestational age | 5.1% vs. 5.3% | Change in HbA1c from 28–37 weeks | Adjusted between-group differences: HbA1c (%), –0.4 (P=0.006) | |
| Macrosomiad: OR, 1.0 (P=NA) | ||||||||
| Alfadhli et al. (2016) [38] | RCT | 130 GDM | Initially not on insulin therapy | 3–7 days of rt-CGM (Guardian REAL-Time) wear within 2 weeks of GDM diagnosis | 5.6% vs. 5.9% | Change in HbA1c, FPG, and PP1 | HbA1c (%): 5.7 vs. 6.1 (P=0.168) | |
| FPG (mg/dL): 85 vs. 90 (P=0.09) | ||||||||
| PP1 (mg/dL): 103 vs. 113 (P=0.057) | ||||||||
| Macrosomiad: No difference between groups | ||||||||
| Yu et al. (2014) [39] | RCT | 340 GDM | Initially not on insulin therapy | 3 days of blinded CGM (Medtronic Minimed) wear every 2–4 weeks | 5.3% vs. 5.3% | Difference in mean glucose and glycemic variability in the 5th week of the study | Mean glucose (mg/dL): 103 vs. 103 (P=0.253) | |
| SD (mg/dL): 14.4 vs. 19.8 (P<0.001) | ||||||||
| TAR>140 mg/dL (%): 0 vs. 4.2 (P<0.001) | ||||||||
| Subjects with TBR<60 mg/dL >30 min/day (%): 3.4 vs. 19.4 | ||||||||
| Macrosomiad: 4.1% vs. 10.8% (P=0.025) | ||||||||
| Preeclampsia: 3.4% vs. 10.1% (P=0.019) | ||||||||
CGM, continuous glucose monitoring; HbA1c, hemoglobin A1c; SMBG, self-monitoring blood glucose; RCT, randomized controlled trial; T1D, type 1 diabetes; MDI, multiple daily insulin injections; rt-CGM, real-time continuous glucose monitoring; TIR, time in range; LGA, large for gestational age; NICU, neonatal intensive care unit; T2D, type 2 diabetes; GDM, gestational diabetes mellitus; HR, hazard ratio; OR, odds ratio; is-CGM, intermittent scanning continuous glucose monitoring; FPG, fasting plasma glucose; PP1, postprandial glucose 1 hour; CI, confidence interval; NA, not applicable; SD, standard deviation; TAR, time above range; TBR, time below range.
Time in target ranging from 63 to 140 mg/dL;
LGA was defined as birth weight percentile >90th;
LGA was defined as birth weight >2 SD above the expected birthweight for gestational age;
Macrosomia was defined as birth weight ≥4,000 g.