Medical Nutrition Therapy for Gestational Diabetes Mellitus
Manual of Clinical Nutrition Management C- 18 Copyright © 2 013 Compass Group, Inc.
Table C-6: Blood Glucose Goals in Gestational Diabetes Mellitus
Time of Measurement Capillary-Blood Glucose
(mg/dL)
Fasting <95
1 - h postprandial <140
2 - h to 6-h postprandial <120
Source: Metzger BE, Buchanan TA, Coustan DR, de Levia A, Dunger DB, Hadden DR et al. Summary and recommendations of
the Fifth International Workshop Conference on Gestational Diabetes Mellitus. Diabetes Care. 2007;30(suppl. 2): S251-
S260.
For women with pre-existing type 1 or type 2 diabetes who become pregnant, the following are suggested
optimal glycemic goals, if they can be achieved without excessive hypoglycemia (1):
Premeal, bedtime, and overnight glucose 60 to 99 mg/dL
Peak postptrandial glucose 100 to 129 mg/dL^
A1C < 6.0%^
Source: Kitzmiller JL, Block JM, Brown FM, Catalano PM, Conway DL, Coustan DR et al. Managing preexisting diabetes for pregnancy:
summary of evidence and consensus recommendations for care. Diabetes Care. 2008;31:1060-1079.
The newer models of glucose meters are often plasma calibrated. Plasma-calibrated meters usually read
10% to 15% higher than whole-blood glucose meters. Therefore, healthcare providers and patients should be
aware of which test is being used to measure glucose levels (4,5). Plasma meters also allow the patient to test
glucose levels at other sites, such as the thigh, arm, or calf. To account for differences in blood glucose levels
from different sites, plasma glucose is measured instead of whole-blood glucose because the values are more
consistent from site to site.
Medication Management
Research indicates that pharmacological therapy, such as the use of insulin, insulin analogs and glyburide, improves
glycemic control and reduces the incidence of poor maternal and neonatal outcomes (Grade II) (6). Insulin therapy is
recommended if medical nutrition therapy fails to maintain the following self-monitored glucose levels: a
fasting plasma glucose level of ≤105 mg/dL, a 1-hour postprandial blood glucose level of <155 mg/dL, and/or
a 2-hour postprandial plasma glucose level of ≤130 mg/dL (Grade I) (6). Human insulin should be used when
insulin is prescribed, and self-monitoring blood glucose records should guide the dosage and timing of insulin
therapy. If insulin therapy is added to nutrition therapy, a primary goal must be to maintain consistent
carbohydrate intake at meals and snacks to facilitate insulin adjustments (4). The prevention of ketosis may
require multiple daily insulin injections and the distribution of dietary carbohydrate into small frequent
meals (three meals and three or four snacks). Insulin requirements normally increase as the pregnancy
proceeds, and the insulin regimen must be continually adjusted throughout the pregnancy. Blood glucose
monitoring by the patient is an essential part of this process (4,5,11). The heightened insulin requirement will
plummet within hours of delivery. Metabolic control during labor, delivery, and the postpartum period
should be managed by frequent determinations of blood glucose levels and adjustments to the insulin dose.
A number of drugs commonly used in the treatment of patients with diabetes may be relatively or
absolutely contraindicated during pregnancy (1). Statins and angiotensin-converting enzyme inhibitors,
which are used to manage disorders in lipid metabolism or hypertension, should be discontinued prior to
conception (1). Among the oral antidiabetic drugs, metformin and acarbose are classified as category B drugs
(no evidence of risk in humans), while all other oral antidiabetic drugs including sulfonylureas (eg, glyburide)
are classified as category C drugs (risk cannot be ruled out) (1,4,5). The potential risks and benefits of oral
antidiabetic agents in the preconception period must be carefully evaluated, recognizing that data are
insufficient to establish the safety of these agents in pregnancy (1). Particularly for patients with preexisting
diabetes, medication evaluation should be carefully assessed as part of preconception care (1).
Physical Activity
Regular physical activity reduces insulin resistance, lowers fasting and postprandial glucose concentrations,
and may be used as an adjunct to nutrition therapy to improve maternal glycemia (Grade II) (4,6). The optimal
frequency and intensity of exercise for lowering maternal glucose concentrations have not been determined;
but, it appears that a minimum of three weekly exercise sessions, each longer than 15 minutes, is required to
modify maternal glucose levels. In addition, 2 to 4 weeks of regular exercise may be required before a
reduction of glycemia occurs (4). Regular physical activity has also been shown to reduce excessive weight