Metformin versus insulin in the management of gestational diabetes mellitus: A meta-analysis
Authors: Ramos Laurice Gizelle Castro , Co-Hidalgo Maribel E. , Zamora Brenda Bernadette B. 
Published: April 2024

OBJECTIVE:
To determine the efficacy of metformin and insulin in the management of gestational diabetes mellitus (GDM).

METHODOLOGY:
Randomized controlled trials (RCT) were retrieved from the databases. All references cited in the articles were also searched by hand to identify additional publications. Studies included were limited to trials on metformin and insulin in the management of GDM in singleton pregnancies. Four RCTs were analyzed in the study. The risk of bias was assessed using Preferred Reporting Items for Systematic reviews and Meta-Analyses Cochrane Collaboration’s tool (Rob 2). Random effects meta-analysis was carried out to pool the data. All analyses were conducted in Review Manager 5.3.5 (2014).

RESULTS:
Meta-analysis of four RCT involving 807 participants (405 were treated with metformin and 402 were treated with insulin) shows that there was no significant difference between metformin and insulin in achieving glycemic control as to fasting blood sugar (FBS), postprandial blood glucose (PPBG), and glycosylated hemoglobin, mean difference (MD) −0.43 (95% confidence interval [CI] −2.77–1.91; P = 0.72), MD −2.13 (95% CI −5.16–0.90, P = 0.17), MD −0.09 (95% CI −0.20–0.02, P = 0.10), respectively. For maternal outcomes, there was a statistically significant 69% decreased risk of hypoglycemia in the metformin group (risk ratio [RR] 0.31, 95% CI 0.20–0.49; P < 0.001). There was no difference in terms of risk of preterm birth (RR 1.11, 95% CI 0.75–1.64, P = 0.60); hypertensive disorders (RR 1.06, 95% CI 0.71–1.60, P = 0.77); polyhydramnios (RR 1.04, 95% CI 0.51–2.14, P = 0.91); and risk of cesarean delivery (RR 0.90, 95% CI 0.75–1.08, P = 0.27). For neonatal outcomes, there was statistically significant 34% reduction on the risk of neonatal hypoglycemia (RR 0.66, 95% CI 0.46–0.94; P = 0.02) in the metformin group. There was no statistical difference in terms of mean birthweight (MD − 81.34, 95% CI −181.69–19.02, P = 0.11). Metformin has decreased the risk of newborns weighing more than 4000 g, babies with birthweight >90th percentile by 27% (RR 0.73, 95% CI 0.28–1.90, P = 0.52), and 20% (RR 0.80, 95% CI 0.54–1.18,
P = 0.26), respectively, but these were not statistically significant. There was no significant difference in terms of risk of birthweight <10th percentile (RR 1.17, 95% CI 0.60–2.31, P = 0.65); APGAR <7 (RR 1.17, 95% CI 0.65–2.08, P = 0.60), birth trauma (RR 0.77, 95% CI 0.23–2.58, P = 0.67), and jaundice requiring phototherapy RR 1.04, 95% CI 0.66–1.65, P = 0.85). Neonatal intensive care unit admission (RR 0.89, 95% CI 0.64–1.23, P = 0.48), respiratory distress syndrome (RR 0.73, 95% CI 0.36–1.50, P = 0.39), transient tachypnea (RR 0.78, 95% CI 0.27–2.19, P = 0.63), and any congenital anomaly (RR 0.58, 95% CI 0.20–1.67, P = 0.31) were decreased in the metformin group but was not statistically significant.

CONCLUSION:
There was no significant difference between metformin and insulin in achieving glycemic control as to FBS and PPBG among patients with GDM. There was a statistically significant reduction in the risk of maternal and neonatal hypoglycemia in the use of metformin.