Unless they have family members with diabetes or there has been some prior discussion of the possibility of the diagnosis, most women will be quite surprised when the test results are positive for GDM, and few will be prepared for the behavioral changes that will be required. Unfortunately, there is no time for "thinking it over." There is only a small window of opportunity to ensure a healthy outcome of the pregnancy. Close monitoring is essential, including multiple daily finger-stick blood sugar measurements (FSBS), careful dietary management, and, possibly, insulin injections. Frequent, often weekly, visits with the physician and sometimes biweekly visits with a diabetic nurse-educator are recommended.
In contrast to nonpregnant patients with diabetes, women with diagnosed GDM measure blood glucose levels before breakfast and then 2 hours postprandially. De Veciana and colleagues found this method to be superior to performing these measurements before meals and at bedtime in terms of decreasing the percentage of LGA babies and the frequency of cesarean delivery. The target FSBS for the 2-hour postprandial values is 120mg/dL. For the fasting test, the acceptable maximal value can range from 95 to 105mg/dL. Even within this fairly narrow range, neonatal outcome varies dramatically. If one chooses 105 mg as the acceptable fasting blood sugar, there is a 28% to 29% incidence of delivering LGA infants. Conversely, with a 95 mg/dL goal, the incidence of LGA infants is approximately 5%. During the initial weeks after diagnosis, close glucose monitoring is recommended. If glucose control within the first weeks is well maintained with a regimen of diet and exercise, the frequency of FSBS measurements may be decreased to a level more acceptable to the patient. If the woman requires insulin, the schedule for FSBS continues with daily fasting and postprandial testing.
By following a slightly modified American Diabetic Association diet and engaging in regular exercise, approximately 85% of women will achieve adequate glucose control.[25,32] Although strict control of the number of kcal/kg/day was proposed in the past, this is not always practical. More general recommendations are now made on the basis of current weight and body mass index (BMI) ( Table 4 ). For example, women of normal weight and medium height should consume 2200 to 2400 kcal/day. Close follow-up with a nutritionist is important.
Exercise is the second component of initial therapy. In addition to promoting general cardiovascular fitness, exercise increases peripheral insulin sensitivity and hepatic glucose uptake. The major concern relating to exercise in pregnancy is its association with uterine contractions and a theoretical risk of subsequent preterm labor or fetal distress. Many exercise regimens have been designed for pregnant women that have not been associated with these complications. Exercises include the arm ergometer, the recumbent bike, and swimming. There is insufficient evidence to recommend a specific type of exercise to manage GDM. The goal of any regimen is to exercise a minimum of 15 minutes at least 3 times a week.
Excellent control (2-hour postprandial glucose level < 120 mg/dL and fasting < 95-105 mg/dL) is usually obtained in the first 2 weeks of adherence to a diet and exercise regimen. If good control is not achieved within the first 2 weeks, or if 2 values per week exceed the target blood sugar levels, control is unlikely to be reached and insulin therapy should be considered.[15,35,36] The ideal insulin regimen is not known. A starting dose of 0.7 U/kg ideal body weight (IBW)/day is often recommended in the first trimester (although women are seldom diagnosed in the first trimester), titrating up to 0.9 U/kg of IBW/day in the third trimester.[32,37] It should be noted that this dosage is based on ideal body weight and not actual weight. As is the case for starting insulin therapy in any newly diagnosed individual, the total dose is divided into 2/3 in the morning and l/3 in the evening. The AM dose is split 2/3 neutral protamine Hagedorn (NPH) insulin and l/3 regular insulin. The PM dose is divided 1/2 regular insulin and 1/2 NPH insulin. The NPH formulation is best given as a bedtime dose. For example, an AM dose of 20U NPH insulin and 10U regular insulin, and a PM dose of 10U of regular insulin followed by 10U NPH insulin at bedtime. Again, the importance of close follow-up cannot be overemphasized. Initially, FSBS done 4 times a day is essential. Many authors recommend daily urine checks for ketonuria, although its value in routine care has not been proven. Insulin lispro, a rapid-acting form of insulin, is an alternative to regular insulin. It may be considered, depending on local practice patterns, as first-line therapy or in consultation with a perinatologist for patients with difficult-to-control gestational diabetes.
The following 2 approaches to GDM care are experimental and should not be considered standard care. They are, however, fascinating. Hopp and colleagues perform amniocentesis when the diagnosis of GDM is made and begin insulin therapy on the basis of the level of insulin detected in the amniotic fluid. Weiss and colleagues[39,40] studied selective amniocentesis based on a screening serum fructosamine level.If elevated, the women underwent amniocentesis for amniotic fluid insulin levels, and insulin needs were determined accordingly. Coetzee and Jackson[41,42,43] in South Africa routinely use Metformin with or without glibenclamide in the treatment of GDM and have published extensively on this treatment approach. Their rate of congenital malformations and severe hypoglycemia, 2 well-known complications of sulfonylureas,[44,45] appear equivalent to those in infants born to mothers with insulin-requiring gestational diabetes.
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Cite this: Gestational Diabetes in Primary Care - Medscape - Feb 23, 2000.