From the Guidelines
For women diagnosed with gestational diabetes mellitus (GDM) solely based on a single abnormal glucose tolerance test, with otherwise normal blood sugar levels, healthy weight, and no other health issues, there is still evidence of increased risk for adverse outcomes, though these risks are lower compared to poorly controlled GDM. Even mild, well-controlled GDM is associated with slightly higher rates of macrosomia (large birth weight), shoulder dystocia, cesarean delivery, and neonatal hypoglycemia, as demonstrated by the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study 1. For the mother, there remains an increased risk of developing type 2 diabetes later in life (about 50% within 5-10 years) 1. The standard management approach still applies:
- blood glucose monitoring
- dietary modifications
- regular exercise are recommended. If blood glucose targets aren't consistently met (fasting <95 mg/dL, 1-hour postprandial <140 mg/dL, 2-hour postprandial <120 mg/dL), medication (typically insulin or sometimes metformin) may be necessary 1. The reason for treating even mild cases is that the placenta produces hormones that increase insulin resistance throughout pregnancy, potentially worsening glucose control as pregnancy progresses 1. Regular monitoring is important because even women with initially excellent control can develop more significant hyperglycemia later in pregnancy 1. Key points to consider include:
- The HAPO study's findings on the continuous increase of risk for adverse maternal, fetal, and neonatal outcomes as a function of maternal glycemia at 24–28 weeks of gestation, even within previously considered normal ranges for pregnancy 1
- The importance of careful reconsideration of the diagnostic criteria for GDM based on these findings 1
- The need for personalized management approaches, taking into account the individual's specific risk factors and health status 1
From the Research
Adverse Health Outcomes for Mother and Baby
- Gestational diabetes mellitus (GDM) is associated with adverse pregnancy outcomes and long-term offspring and maternal complications, including type 2 diabetes mellitus and cardiovascular disease for mothers, and childhood obesity and glucose intolerance for offspring 2.
- The diagnostic criteria of GDM should properly classify women at risk for adverse pregnancy outcomes and long-term complications 2.
Rates of Adverse Health Outcomes
- A study found that early treatment with metformin was not superior to placebo for the composite primary outcome of insulin initiation or a fasting glucose level of 5.1 mmol/L or greater at gestation weeks 32 or 38 3.
- However, secondary outcome data supported further investigation of metformin in larger clinical trials, with prespecified secondary maternal outcomes favoring the metformin group, including time to insulin initiation, self-reported capillary glycemic control, and gestational weight gain 3.
- Another study found that fasting glucose at oral glucose tolerance test (OGTT) was significantly lower in metformin responders versus nonresponders, and that 93% of women with fasting glucose ≤5.2 mmol/L responded to metformin 4.
Management and Treatment Options
- Management strategies for GDM increasingly emphasize optimal management of fetal growth and weight, with monitoring of glucose, fetal stress, and fetal weight through ultrasound combined with maternal weight management, medical nutritional therapy, physical activity, and pharmacotherapy 5.
- A randomized study found that metformin is an effective alternative to insulin in the treatment of GDM patients, with only 20.9% of patients in the metformin group needing additional insulin 6.
- Serum fructosamine may help in predicting the adequacy of metformin treatment alone, with a 4.6-fold increased risk for additional insulin in women with baseline serum fructosamine concentration above median 6.