Gestational Diabetes in Primary Care

Follow-up

The common course of gestational diabetes is complete resolution in the postpartum period, although it can be several days or weeks before the glucose intolerance completely resolves. Paralleling the drop in cortisol level, human placental lactogen (HPL), and estrogen, the insulin requirement declines to 60% of that needed before delivery.^[29] Continuing to check FSBS, either before meals and at bedtime or fasting and postprandially, one can assess the need for continued insulin treatment. Only in rare instances does a woman need insulin on a long-term basis. Usually, if any treatment is required, low-dose oral agents are sufficient. Bear in mind that all the newer oral agents, including Metformin, are excreted in breast milk and have unknown effects on the baby. The American Academy of Pediatrics considers tolbutamide to be compatible with breast-feeding.^[54]

In addition to the immediate management, one must consider the possibility of future development of Type II DM. This risk has been estimated at 30%-50%^[1] (the risk of GDM in a future pregnancy is estimated at 50%-70%).^[47,55,56] Therefore, it is recommended that at the 6-week postpartum visit women have a 2-hour, 75-g GTT. The diagnosis of diabetes is made if fasting plasma glucose is ≥ 126 mg/dL or if the 2- hour level is ≥ 200mg/dL ( Table 6 ). In addition, a random plasma glucose level of ≥ 200 mg/dL is diagnostic of diabetes and requires no confirmatory testing.^[13] If the result of the 2-hour GTT is negative, repeat testing every 3 years may be considered.^[15] Education of the new mother is imperative. It is prudent, given the risk of developing DM, that she be encouraged to continue following a healthy diet appropriate for individuals with diabetes and to participate in regular exercise.

There are no standard guidelines for the follow-up of children from GDM pregnancies. It is known that infants of mothers with pregestational diabetes are at increased risk for obesity and being overweight.^[57,58,59] There is evidence of a similarly increased risk in children born to mothers with GDM.^[60]

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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