Gestational Diabetes in Primary Care

Paul Hicks, MD

Neonatal Complications

In many cases, the physician who provides prenatal care will become the baby's caregiver as well. As such, the neonatal complications of GDM are important to consider. The potential sequelae of shoulder dystocia are Erb's palsy, a stretch injury to the brachial plexus, and intrapartum fetal hypoxia, with the possibility of a hypoxic ischemic event or death if the hypoxia is extreme or prolonged. The flaccid paralysis of Erb's palsy usually resolves in the first few days to weeks but occasionally is lifelong.

Other neonatal complications of GDM are hypoglycemia, polycythemia, and respiratory distress. Secondary to fetal hyperinsulinemia, hypoglycemia is defined as a heel-stick blood sugar < 35 mg/dL in a full-term neonate and < 25 mg/dL in one born preterm. The hypoglycemia typically resolves with feeding of either milk or a glucose solution. If the baby is symptomatic or the hypoglycemia profound, an IV bolus of 10% dextrose is recommended -- 0.25 mg/kg followed by 4-6 mg glucose/kg/min with gradual titration. Blood sugar monitoring is continued every hour until it has stabilized. Polycythemia is a result of chronic intrauterine hypoxemia and placental insufficiency secondary to poor glycemic control. Hypoxemia causes increased fetal erythropoietin release and subsequent polycythemia.^[52] When these extra red blood cells break down, there is increased incidence of hyperbilirubinemia at days to weeks after birth. Respiratory distress is the most serious complication for the neonate. Fetuses affected by GDM are at elevated risk (perhaps 5- to 6-fold greater) of lung immaturity compared with age-matched controls.^[53] Oxygen supplementation, ventilatory support, and surfactant replacement are among the treatments available, and care may require consultation with a neonatologist.

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Cite this: Gestational Diabetes in Primary Care - Medscape - Feb 23, 2000.

Table 1. Composition of Study Population by Race/Ethnicity With 50-g Oral Glucose Screening Test and 3-Hour Glucose Tolerance Test Results
Race/Ethnicity	N	Third-Trimester GST Result* (mg/dL)	Third-Trimester GST Result > 140 mg/dL	GDM Diagnosed in Patients With GST > 140 mg/dL	Prevalence of GDM Diagnosed in Third Trimester
White	654 (71%)	123.2±28.4	27.4%	17.3%	6.0%
Hispanic	512 (56%)	123.2±28.3	26.8%	18.2%	6.3%
Non-Hispanic	142 (15%)	123.5±28.5	29.6%	14.3%	4.9%
Black	120 (13%)	116.4±31.6	17.5%	42.9%	7.5%
Filipino	83 (9%)	127.6±26.3	31.3%	11.5%	3.6%
Asian^†	64 (7%)	134.7±25.0	40.6%	11.5%	4.7%

GST = to-g oral glucose screening test
*Mean + SD.
^†Asian includes subjects of Chinese, Japanese, Korean, Vietnamese, Thai, Cambodian, and Laotian ethnicity.; Reprinted with permission from Nahum and Huffaker.^[14]

Table 2. Recommended Race-Specific Glucose Screening Test Thresholds for Initiating 3-Hour Glucose Tolerance Testing, With Expected Yields of Positive Results by Race
	Blacks	Whites	Filipinos	Asians
Recommended upper limit threshold for normalcy of GST result (mg/dL)*	130	140	145	150
Expected proportion of gravidas exceeding threshold limit	24.2%	27.4%	27.7%	23.4%
Expected percentage of gravidas diagnosed with GDM in third trimester	7.5-8.3%	4.7%	3.6%	3.1%

*Plasma glucose oxidase values; Reprinted with permission from Nahum and Huffaker.^[14]

Table 3. Detection of Gestational Diabetes*
100-g oral glucose tolerance test	O'Sullivan Criteria	Carpenter Conversion
Fasting	105	95
1-hour	190	180
2-hour	165	155
3-hour	145	140

*Diagnosis of gestational diabetes is made when any 2 values are met or exceeded.; Reprinted with permission from American College of Obstetricians and Gynecologists.^[1]

Table 4. Caloric Restrictions in Obese and Nonobese Women With GDM
Distribution of Calories in a Diabetic Diet
Breakfast = 20% total kcal/day
Lunch = 25%
Supper = 25%
3 snacks, after each meal = 5% each
1 snack before bed = 15%

Adapted from Langer and Hod.^[29]

Table 5. Low-Dosage Constant Insulin Infusion for the Intrapartum Period*
Blood Glucose (mg/100 mL)	Insulin Dosage (U/hr)	Fluids (125 mL/hr)
< 100	0	Dextrose/Lactated Ringer's
100-140	1.0	Dextrose/Lactated Ringer's
141-180	1.5	Normal saline
181-220	2.0	Normal saline
> 220	2.5	Normal saline

*Dilution is 25 U of regular insulin in 250 mL of normal saline with 25 mL flushed through line administered intravenously. A finger-stick glucose test is performed every 1-2 hours. The insulin pump and intravenous solution are adjusted accordingly.; Adapted from Hollingsworth and Moore.^[62]

Table 6. Postpartum Evaluation for Carbohydrate Intolerance
Plasma glucose level*(mg/dL) in
Time Tested	No Diabetes	Impaired Glucose Tolerance	Diabetes Mellitus
Fasting	< 110	>/= 110 and < 126	>/= 126
2 h	< 140	140-199	>/= 200

*Values are based on a 2-h, 75-g oral glucose tolerance test.; Reprinted with permission from the American Diabetes Association.^[16]

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Gestational Diabetes in Primary Care

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