Updated: 9/14/2020

Gestational Diabetes

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  • Snapshot
    • A 33-year-old G3P2 woman at 24 weeks gestation presents to the clinic for a routine prenatal visit. Fundal height measures 33 cm. She is scheduled for an oral glucose tolerance test due to her fetus being large for gestational age (see chart in image). Her 1-hour postprandial glucose level is 215 mg/dL, 2-hour postprandial glucose level is 185 mg/dL, and 3-hour postprandial glucose level is 146 mg/dL.
  • Introduction
    • Overview
      • gestational diabetes mellitus is a condition characterized by glucose intolerance that is first recognized during pregnancy
  • Epidemiology
    • Prevalence
      • occurs in approximately 6% of pregnant women in the US
    • Risk factors
      • obesity
      • family history of diabetes mellitus
      • maternal age > 30
      • having previously given birth to an infant weighing > 9 pounds
      • polycystic ovary syndrome
      • non-white race
    • Pathophysiology
      • ↑ hormones of pregnancy (i.e., estrogen, cortisol, and human placental lactogen) may ↑ risk of insulin resistance
  • Presentation
    • Symptoms
      • asymptomatic in majority of cases
      • increased thirst and ↑ frequency of urination
    • Physical exam
      • fetus size large for gestational age
  • Studies
    • Oral glucose tolerance test
      • conduct a 1-hour 50 g oral glucose tolerance test
        • measure venous plasma glucose after 1 hour
        • perform at 24-28 weeks of gestation
        • ≥ 140 mg/dL is considered abnormal
      • conduct an oral 3-hour 100 g glucose tolerance test
        • confirm abnormal test if any 2 of the following are present
          • fasting glucose level > 95 mg/dL
          • glucose level after 1 hour > 180 mg/dL
          • glucose level after 2 hours > 155 mg/dL
          • glucose level after 3 hours > 140 mg/dL
  • Treatment
    • Lifestyle
      • strict adherence to a diabetic diet (eating healthy foods rich in vitamins, minerals, and fiber and adhering to regular mealtimes and moderate portion sizes)
        • indications
          • initial treatment
      • aerobic exercise and resistance training
        • indications
          • initial treatment
      • routine monitoring of fasting blood glucose and postprandial glucose levels
        • indications
          • initial treatment
    • Medical
      • insulin
        • indications
          • elevated blood glucose level despite lifestyle modifications
      • metformin
        • indications
          • elevated blood glucose level despite lifestyle modifications
      • glyburide
        • indications
          • elevated blood glucose level despite lifestyle modifications
  • Complications
    • Maternal complications
      • ↑ risk of developing type II diabetes mellitus
      • ↑ risk of developing cardiovascular disease
    • Fetal complications
      • perinatal mortality
        • incidence
          • 2-5% of babies born to mothers with gestational DM
      • neonatal hypoglycemia
        • ↑ amount of fetal insulin in the setting of a ↑ maternal glucose supply in utero
          • ß-cell hyperplasia in the newborn
      • congenital defects
        • cardiac deformities
          • secondary to trophic effect of insulin
        • macrosomia (> 4500 g)
          • shoulder dystocia during vaginal delivery
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(M2.OB.17.4740) A 37-year-old G1P1001 delivers a male infant at 9 pounds 6 ounces after a C-section for preeclampsia with severe features. The mother has a history of type II diabetes with a hemoglobin A1c of 12.8% at her first obstetric visit. Before this pregnancy, she was taking metformin, and during this pregnancy, she was started on insulin. At her routine visits, her glucose logs frequently showed fasting fingerstick glucoses above 120 mg/dL and postprandial values above 180 mg/dL. In addition, her routine third trimester culture for group B Streptococcus was positive. At 38 weeks and 4 days gestation, she was found to have a blood pressure of 176/103 mmHg and reported a severe headache during a routine obstetric visit. She denied rupture of membranes or vaginal bleeding. Her physician sent her to the obstetric triage unit, and after failure of several intravenous doses of labetalol to lower her blood pressure and relieve her headache, a C-section was performed without complication. Fetal heart rate tracing had been reassuring throughout her admission. Apgar scores at 1 and 5 minutes were 7 and 10. After one hour, the infant is found to be jittery; the infant's temperature is 96.1°F (35.6°C), blood pressure is 80/50 mmHg, pulse is 110/min, and respirations are 60/min. When the first feeding is attempted, he does not latch and begins to shake his arms and legs. After 20 seconds, the episode ends and the infant becomes lethargic. Which of the following is the most likely cause of this infant’s presentation?

QID: 108655

Transplacental action of maternal insulin



ß-cell hyperplasia



Neonatal sepsis



Inborn error of metabolism



Neonatal encephalopathy



M 6 D

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