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CLINICAL DIABETESVOL. 17 NO. 3 1999

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CASE STUDIES

Case Study: A 34-Year-Old Woman in Her

Second Pregnancy at 24 Weeks Gestation

Steven G. Gabbe, MD

Presentation

A 34-year-old Hispanic-American woman who is in her second pregnancy and has had

one live birth and no abortions is seen for prenatal care at 24 weeks gestation. Her weight

is 220 lb, and her blood pressure is 130/80 mmHg. Uterine size is appropriate for

gestational age. The patient's past obstetric history includes the spontaneous vaginal

delivery of a 9 lb, 8 oz. male infant at 40 weeks gestation, 8 years ago in Mexico. The

patient reports that the child is doing well. Her family history reveals that her mother hastype 2 diabetes mellitus. A urine dipstick shows 3+ glycosuria and negative ketones.

Questions

1. What tests should be done to evaluate the patient's glucose tolerance?

2. How is the diagnosis of gestational diabetes mellitus (GDM) established?

3. What would be the best treatment and follow-up strategy?

Commentary

This patient presents with several risk factors for GDM, defined as carbohydrateintolerance of varying degrees of severity with onset or first recognition during pregnancy,

regardless of whether insulin is used for treatment or the condition persists after pregnancy.

She is over 30 years of age, from an ethnic group at increased risk for type 2 diabetes

mellitus, is obese, and has a first-degree relative with type 2 diabetes.

The findings of significant glycosuria should prompt the performance of a glucose

determination before the patient leaves the clinic. The usual approach to screening would

be a 50-g oral glucose load administered to the patient between 24 and 28 weeks

gestation when the "diabetigenic stress" of pregnancy is present. A positive test is a venous

plasma glucose value 1 hour later of > 140 mg/dl. This would lead to a 100-gm oral

glucose tolerance test (OGTT) with the diagnosis of GDM made if two of the following

values are met or exceeded: fasting, 95 mg/dl; 1-hour, 180 mg/dl; 2-hour, 155 mg/dl; and

3-hour, 140 mg/dl. These cutoff values are those proposed by Carpenter and Coustan and

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recommended most recently by the Fourth International Workshop-Conference on

Gestational Diabetes Mellitus and the American Diabetes Association.

The patient's capillary glucose reading, performed in the clinic, was 193 mg/dl. She was

instructed to return the next morning for a fasting venous plasma glucose, which was 143

mg/dl. Given this finding, the diagnosis of GDM was established. While it is likely that the

patient had diabetes before pregnancy, given the significant elevation of her fasting glucose

level, this is GDM because its first recognition was during pregnancy. There is no need toperformfurther testing in this patient. A single elevated fasting glucose of >126 mg/dl

obviates further testing. A glycohemglobin could be performed, and, if elevated, supports

the likelihood of pre-existing diabetes mellitus.

The patient was begun on both dietary and insulin therapy as an outpatient. Her diet

included 25 kcal/kg actual body weight divided into three meals and a bedtime snack. The

diet emphasized complex carbohydrates with the avoidance of simple carbohydrates. In

addition, she was instructed on self-monitoring of blood glucose, performing tests while

fasting and 2 hours after each meal. The targets for therapy were a fasting value of < 95

mg/dl and values no higher than 140 mg/dl at 1 hour or no higher than 120 mg/dl at 2

hours after eating. She was started empirically on 20 U of NPH and 10 U of regular insulin

administered in the morning, to be adjusted after reviewing her glucose log sheets. The

patient was seen each week. Given the significant elevation of her fasting glucose level, a

trial of diet only was not advisable.

The patient did well on this regimen, maintaining good control until 30 weeks gestation,

when her total insulin dose was increased by 20%. At 28 weeks, the patient was

instructed in daily fetal movement counting to assess fetal well-being, and at 32 weeks

gestation antepartum fetal heart rate testing with nonstress tests was begun twice weekly.An ultrasound examination at 37 weeks revealed the fetus to be growing normally with an

estimated weight of 7 lb, 1 oz. At 39 weeks, the patient started spontaneous labor and

underwent the vaginal delivery of an 8 lb, 1 oz boy. The infant was evaluated for but did

not demonstrate hypoglycemia or other morbidities.

Postpartum, the patient breastfed her infant and, with her partner, decided on a barrier

method of contraception: foam and condoms. Six weeks after delivery, she returned to the

clinic for an evaluation of her glucose tolerance. Her fasting plasma glucose was 128

mg/dl. She returned the next day, and a repeat fasting plasma glucose was 132 mg/dl.

Given these findings, the diagnosis of diabetes mellitus was made, and a 75-g OGGT test

was not needed.

Clinical Pearls

1. When patients present with significant risk factors for GDM, early

screening for GDM, before 20 weeks gestation, might be undertaken.

2. The finding of glycosuria should prompt a random capillary glucose

performed immediately and a follow-up fasting venous plasma glucose.

3. Given an elevated fasting venous plasma glucose, such patients should be

started immediately on diet and insulin therapy and followed with self-

monitoring of blood glucose using the criteria recommended by the Fourth

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International Workshop-Conference on Gestational Diabetes Mellitus.

4. Patients treated with not only diet but also insulin are at increased risk for

an intrauterine fetal death, and for that reason, antepartum fetal testing with

nonstress tests should be performed.

5. For such patients who do not enter spontaneous labor, induction of labor

at 39 weeks is appropriate.

6. Postpartum, this patient was found to have an elevated fasting plasma

glucose and the diagnosis of diabetes mellitus was made. That diabetes

persisted after delivery is not surprising given that the diagnosis of GDM was

made relatively early in pregnancy, that the fasting plasma glucose exceeded

140 mg/dl, and that the patient was obese.

SUGGESTED READINGS

Carpenter MW, Coustan DR: Criteria for screening tests for gestational diabetes.Am J

Obstet Gynecol144:76873, 1982.

Expert Committee on the Diagnosis and Classification of Diabetes Mellitus: Report of the

expert committee on the diagnosis and classification of diabetes mellitus.Diabetes Care

20:118297, 1997.

Gabbe SG, Mestman JH, Freeman RK, Anderson GV, Lowensohn RI: Management and

outcome of Class A diabetes mellitus.Am J Obstet Gynecol127:46569, 1977.

Gregory KD, Kjos SL, Peters RK: Cost on non-insulin-dependent diabetes in women

with a history of gestational diabetes: implication for prevention. Obstet Gynecol

81:18286, 1993.

Kjos SL, Buchanan TA, Greenspoon JS, Montoro M, Bernstein GS, Mestman JH:

Gestational diabetes mellitus: the prevalence of glucose intolerance and diabetes mellitus in

the first two months postpartum.Am J Obstet Gynecol163:9398, 1990.

Metzger BE, Coustan DR, The Organizing Committee: Proceedings of the Fourth

International Workshop-Conference on Gestational Diabetes Mellitus.Diabetes Care21(Suppl. 2):B16167, 1998.

American Diabetes Association: Position statement: Standards of medical care for patients

with diabetes mellitus.Diabetes Care 22(Suppl. 1): S3241, 1999.

Steven G. Gabbe, MD, is a professor and chair of the Department of Obstetrics and

Gynecology at the University of Washington School of Medicine in Seattle.

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