gestational diabetes

Etiology

• no strong evidence supports a causal effect of vitamin D status on gestational hypertension or pre-eclampsia
• antidepressant use during pregnancy
  • RR= 1.2; SNRI RR=1.3; tricyclic antidepressants RR=1.5; venlafaxine RR=1.3; amitriptyline RR=1.5

Epidemiology

• 2-4% of pregnancies with prevalence increasing
• 7% of pregnancies
• higher incidence in Native Americans, blacks & hispanics

Pathology

• insulin-resistance
  • normally develops in 3rd trimester
  • inadequately compensatated by islet cell hyperfunction

Clinical manifestations

• develops around 7th month of pregnancy

Laboratory

Step 1 glucose tolerance test*

• 50 grams of oral glucose
  • 1 hour serum glucose > 140 mg/dL, proceed to step 2

Step 2 glucose tolerance test

• 100 grams of glucose load
  • fasting serum glucose > 95 mg/dL
  • 1 hour serum glucose > 180 mg/dL
  • 2 hour serum glucose > 155 mg/dL
  • 3 hour serum glucose > 140 mg/dL
• positive test is 2 or more criteria met

* All pregnant women should be screened after 24 weeks

Complications

• maternal risks
  • 50% will develop type-2 diabetes within 5-10 years
• fetal risks (treatment reduces serious risk)
  • intrauterine death
  • acute respiratory distress syndrome
  • hypoglycemia*
  • hypocalcemia
  • polycythemia*
  • hyperviscosity
  • hyperbilirubinemia (develops after birth)
  • cardiomyopathy
  • macrosomia (most common)
  • shoulder dystocia
  • bone fracture
  • nerve palsy
• treatment reduces preeclampsia, shoulder dystocia, & macrosomia
• increased risk of autism in offspring (RR=1.42)
• progression to type 2 diabetes
  • breast feeding may lower risk
• gestational diabetes increases maternal risk of cardiovascular disease
  • healthy lifestyle habits in midlife may mitigate this risk
• increased risk of early-onset cardiovascular disease in offspring (RR=1.2)

* risk at birth

• disease interaction(s) of obesity with gesational diabetes

Management

• goals:
  • fasting blood glucose < 90 mg/dL
  • 1 hour post-prandial glucose < 120 mg/dL
• successfully treated with diet in most patients
  • avoid ketosis associated with carbohydrate deprivation
  • Mediterranean diet may lower risk for gestational diabetes
• insulin is probably safest choice if diet ineffective
• oral hypoglycemics may see more use
  • metformin is probably safe
    • associated with higher incidence of preterm birth than insulin
    • long-term outcomes associated with metformin are still uncertain
    • metformin appears to be a reasonably safe alternative to insulin for patients who refuse insulin
  • glyburide
    • should not be used in pregnant women
    • somewhat more effective than metformin in controlling hyperglycemia in mom
    • may be an acceptable agent for women unable to tolerate insulin
    • excess risk for adverse neonatal outcomes with glyburide
    • associated with higher rates of macrosomia & neonatal hypoglycemia than insulin or metformin
    • increased risk for neonatal ICU admission (10.2 vs 7.2%), respiratory distress (2.9 vs 1.7%), hypoglycemia (1.9% vs 1.3%), birth injury (2.2 vs 1.6%), & macrosomia (4.7 vs 3.2%) relative to treatment with insulin
    • composite outcome of macrosomia, neonatal hypoglycemia, & hyperbilirubinemia 27.6% with glyburide vs 23.4% with insulin
  • GLP-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, or flozins not associated with increased risk of birth defects
• hypoglycemia is common, but NOT clearly associated with risk to fetus
• screening:
  • all pregnant women should be screened after 24 weeks of gestation
  • women with risk factors should be screened at the onset of gestation
• eye examination once per trimester
• prevention:
  • healthy lifestyle factors (regular exercise, normal weight, healthy diet, no smoking) may reduce risk by at least 40%
  • in obese women, myo-inositol 4 grams daily may reduce risk of gestational diabetes
• followup
  • screening for diabetes at 6-12 weeks postpartum & every 3 years thereafter; annual screening

More general terms

• pregnancy disorder; obstetric disorder; pregnancy complication
• diabetes mellitus

Additional terms

• diabetics who become pregnant
• glucose challenge (tolerance) test

Patient information

gestational diabetes patient information