Metformin-treated-GDM has lower risk of macrosomia compared to diet-treated GDM- a retrospective cohort study

Background: The diagnosis of gestational diabetes (GDM) has undergone several revisions. The broad adoption of the 2013 WHO criteria for hyperglycemia in pregnancy has increased the prevalence of GDM with no apparent benefit on pregnancy outcomes. The study aims to investigate the pregnancy outcomes in women with GDM diagnosed based on the WHO criteria compared to a control group; the impact of other confounders; and the difference in outcomes between GDM women who needed pharmacotherapy (GDM-T) and those who did not (GDM-D).Methods: This is a retrospective cohort study that included GDM women compared to normoglycemic controls between March 2015 and December 2016 in the Women's Hospital, Qatar.Results: The study included 2221 women; of which 1420 were normoglycemic, and 801 were GDM (358 GDM-D and 443 GDM-T). At conception, GDM women were older (mean age 32.5 ± 5.4 versus 29.6 ± 5.6 years, p<.001) and had higher prepregnancy BMI (mean BMI 32.2 ± 6.2 versus 28.2 ± 6.1 kg/m2, p<.01) compared to the controls, respectively. After correction for age, prepregnancy weight, and gestational weight gain (GWG); women with GDM had a higher risk of preterm labor (OR: 1.72; 95% CI: 1.32-2.23), large for gestational age (GA) (OR: 1.67; 95% CI: 1.22-2.29), neonatal ICU admission (OR: 1.57; 95% CI: 1.15-2.13), and neonatal hypoglycemia (OR: 3.22; 95% CI: 2.06-5.03). At conception, GDM-T women were older (mean age 33.3 ± 5.0 versus 31.5 ± 5.7 years, p<.001) and had higher BMI (mean BMI 32.9 ± 6.3 versus 231.2 ± 6.0 kg/m2, p=.01) compared to GDM-D, respectively. Metformin was used in 90.7% of the GDM-T women. Women in the GDM-T group had lower GWG/week compared to GDM-D (-0.01 ± 0.7 versus 0.21 ± 0.5 kg/week; p<.001). After correcting for age, prepregnancy weight and GWG; GDM-T had a higher risk of preterm labor (OR: 1.66; 95% CI: 1.20-2.22), and C-section (OR: 1.37, 95% CI: 1.02-1.85) and reduced risk of macrosomia (OR: 0.56; 95% CI: 0.32-0.96) and neonatal hypoglycemia (OR: 0.49; 95% CI: 0.28-0.82).Conclusion: In addition to hyperglycemia, the adverse effects of GDM on pregnancy outcomes are multifactorial and includes maternal age, maternal obesity, and gestational weight gain. Treatment with metformin reduces maternal weight gain, the risk of macrosomia and neonatal hypoglycemia compared to diet alone.