Gestational diabetes

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Gestational diabetes is a type of diabetes that onsets or is first recognized during pregnancy in the reproductive female. It is characterized by persistent hyperglycemia and glucosuria. Prevalence ranges from 3.7% in the non-aboriginal population to as high as 18% in aboriginals.

Risk factors

  • Age greater than 25 years
  • A family history of diabetes, especially in first degree relatives
  • Prepregnancy weight ≥110 percent of ideal body weight or body mass index over 30 kg/m2 or significant weight gain in early adulthood, between pregnancies, or in early pregnancy
  • Previous delivery of a baby greater than 4 kg
  • Personal history of abnormal glucose tolerance
  • Member of an ethnic group with higher than the background rate of type 2 diabetes (in most populations, the background rate is approximately 2 percent)
  • Previous unexplained perinatal loss or birth of a malformed child
  • Maternal birthweight greater than 4kg or less than 2.7 kg
  • Glycosuria at the first prenatal visit
  • Polycystic ovary syndrome
  • Current use of glucocorticoids
  • Essential hypertension or pregnancy-related hypertension


Screening

Opinions vary, but general recommendation is to screen all women at 24-28 weeks gestation.

To screen for gestational diabetes, a 50 gram oral glucose load is given any time during the day irrespective of prandial state at 24-28 weeks gestation. Blood sugar is measured one hour after the glucose drink. Cut offs of 7.2 or 7.8mmol can be used. A cut off of 7.2 is considered 100% sensitive, whereas a cutoff of 7.8 is about 90% sensitive. Diabetes can be comfortably diagnosed if the reading is ≥ 10.3, though definitive diagnosis involves a 75 gram oral glucose challenge with measurements at three intervals (fasting ≤ 5.3, 1h post ≤ 10.6, and 2h post ≤ 8.9). One abnormal value indicates impaired glucose tolerance of pregnancy, while two abnormal values result in a diagnosis of gestational diabetes.

Treatment

Treatment of gestational diabetes includes a special diet, blood sugar monitoring, and insulin therapy if necessary. The targets of treatment are as in the table below.

Fasting and preprandial PG 3.8–5.2 mmol/L
1h postprandial PG 5.5–7.7 mmol/L
2h postprandial PG 5.0–6.6 mmol/L
HgA1C ≤6.0% (normal)