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Diabetes

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Gestational Diabetes

Gestational diabetesis a form of high blood glucose (hyperglycemia) seen in some pregnant women, usually late in their pregnancy. The cause is unknown, but it is thought that some hormones from the placenta increase insulin resistance in the mother, causing elevated blood glucose levels. Those at an increased risk include women who:

  • Are overweight
  • Have had gestational diabetes with a previous pregnancy
  • Are older than 25 years
  • Have previously had a very large baby or have had a stillbirth
  • Have a close relative who has diabetes
  • Have polycystic ovary syndrome (PCOS)
  • Are of African American, Hispanic American, Native American, Asian American, or Pacific Islander ethnicity

Most women are screened for gestational diabetes between their 24th and 28th week of pregnancy. If gestational diabetes is found and not addressed, the baby is likely to be larger than normal, be born with low glucose levels, and be born prematurely. It can also cause complications such as high blood pressure and pre-eclampsia in the pregnant woman.

The hyperglycemia associated with gestational diabetes usually goes away after the baby's birth, but both the women diagnosed with gestational diabetes and their babies are at an increased risk of eventually developing type 2 diabetes. A woman who has gestational diabetes with one pregnancy will frequently experience it with subsequent pregnancies.

Signs and Symptoms

Signs and symptoms of gestational diabetes correspond to those of diabetes in general (see the section on Signs and Symptoms). Some women with gestational diabetes may not have any noticeable symptoms and may be unaware that they have developed the condition.

Laboratory Tests

Most professional organizations recommend screening pregnant women for gestational diabetes with a blood test at 24-28 weeks of pregnancy. The American Diabetes Association recommends that pregnant women not previously known to have diabetes be screened and diagnosed, using either a one-step or two-step approach. The American College of Obstetricians and Gynecologists recommends the two-step approach.

  • One-step approach:
    • Perform an oral glucose tolerance test (OGTT). After a fasting glucose level is measured, a woman is given a 75-gram dose of glucose to drink and her glucose levels are measured at 1 hour and 2 hours after the dose. Only one of the values needs to be above a cutoff value for diagnosis:
    Time of Sample Collection Glucose Result
    Fasting Equal to or greater than 92 mg/dL (5.1 mmol/L)
    1 hour after glucose drink Equal to or greater than 180 mg/dL (10.0 mmol/L)
    2 hours after glucose drink Equal to or greater than 153 mg/dL (8.5 mmol/L)
  • Two-step approach:
    • Perform a glucose challenge test as a screen. A woman is given a 50-gram glucose dose to drink and her blood glucose level is measured after 1 hour. A value of 140 mg/dL (7.8 mmol/L) or greater (or some experts recommend a cutoff of 130 mg/dL (7.2 mmol/L)) is abnormal and indicates the need for a 3-hour OGTT (see below).
    • If the challenge test is abnormal, perform a 3-hour OGTT. After a woman's fasting glucose level is measured, she is given a 100-gram glucose dose and her glucose level is measured at timed intervals. If at least two of the glucose levels at fasting, 1 hour, 2 hour, or 3 hour are above a certain level, then a diagnosis of gestational diabetes is made.
    Time of Sample Collection Target Levels**
    (**some labs may use different numbers)
    Fasting (prior to glucose load) 95 mg/dL (5.3 mmol/L)
    1 hour after glucose load 180 mg/dL (10.0 mmol/L)
    2 hours after glucose load 155 mg/dL (8.6 mmol/L)
    3 hours after glucose load 140 mg/dL (7.8 mmol/L)

Women who are diagnosed with gestational diabetes should be tested at 6-12 weeks after they have delivered their baby to screen for persistent diabetes. This can be done with one of the following:

  • A fasting blood glucose
  • A 2-hour oral glucose tolerance test (OGTT)
  • An A1c test

Treatment

With gestational diabetes, the mother-to-be will need to eat a modified diet, get regular exercise, and monitor glucose levels as often as her health practitioner suggests. If more control is needed, she will be given insulin injections. At this time, oral medications are not commonly used.

Usually, the diabetic state resolves after the birth of the baby, although the woman remains at a higher risk of becoming a type 2 diabetic and she should be carefully monitored with any subsequent pregnancies. Right after birth, her baby will be monitored for signs of low blood glucose (hypoglycemia) and for any trouble breathing (respiratory distress).

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