- The Best Time to Check Blood Glucose After a Meal
- Why Checking Postprandial Glucose Is Important
- What Else You Should Know About Postprandial Glucose
- How Knowing Your PPG Can Give You Control Over Your Diabetes
- Who Should Check PPG?
- How to Test PPG
- post prandial blood sugar test Test
- Introduction to Postprandial Blood Sugar
- Why is Postprandial Blood Glucose Important?
- How is the Test Performed?
- How Should You Take Care of After-Meal Spikes?
- Why Should You Keep an Eye on Postprandial Blood Glucose?
- The 6E Approach to Person-centered Care
- Management of Gestational Diabetes Mellitus
- Management of Gestational Diabetes
The Best Time to Check Blood Glucose After a Meal
Q: I was recently diagnosed with type 2 diabetes. Should I check my blood glucose two hours from when I start eating or after I finish eating my meal?
A: Most of the food you consume will be digested and raises blood glucose in one to two hours. To capture the peak level of your blood glucose, it is best to test one to two hours after you start eating.
Don’t Miss: Packable Diabetes-Friendly Salads
The American Diabetes Association recommends a target of below 180 mg/dl two hours after a meal. The American Association of Clinical Endocrinologists recommends a lower target: below 140 mg/dl two hours after a meal.
Ask your doctor which target is right for you. Postmeal blood glucose monitoring (and record-keeping) is important because it helps you see how your body responds to carbohydrates in general and particular foods. Managing postmeal blood glucose can help reduce your risk of developing heart and circulation problems.
Virginia Zamudio Lange, a member of Diabetic Living’s editorial advisory board, is a founding partner of Alamo Diabetes Team, LLP in San Antonio.
The preferred time to test blood sugar isn’t before breakfast any more. Researchers looking at studies of hundreds of people with type 2 diabetes suggest that high blood glucose levels after meals has a greater effect on A1C levels among people who have their diabetes under good control than among those with poor control.
When A1C results are low – less than 7.3 percent – mealtime glucose contributes about 70 percent of the A1C. However, when A1C results are high – greater than 10.2 percent – fasting blood glucose contributes 70 percent of the A1C value.
If your A1C levels are above 7.0 percent, you run a much greater risk of complications. That means getting your diabetes under control needs to be your top priority. After you do that, you can concentrate on testing after meals.
But do we start counting from the beginning, the middle, or the end of the meal? And should we test one, two, or more hours after eating?
There is a great variation in the length of a meal. So it is more precise to start counting from the time of the first bite. Another reason to start counting from the beginning of a meal is because our glucose levels begin to rise about 10 minutes after the start of a meal.
Both organizations recommend that most of us test two hours after eating. While your blood glucose level could be highest one hour after a meal, there are good reasons to wait until two hours after the first bite. Writing on a diabetes mailing list, someone called Helen said it best:
“If I aim for pre-meal levels to occur an hour after eating, I chance going low after two hours and for sure after three hours. My blood glucose level tends to decline from hour two to hour three. Therefore I do not test one hour after – there is nothing I would do with that information other than aggravate myself.”
The exception, according to the ADA, is women who have diabetes and are pregnant. They could benefit more from testing one hour after eating.
The point of testing is to help you bring your levels down. Talk with you doctor about how often you should be testing your blood glucose to avoid overuse.
Several different organizations have set targets for blood glucose levels two hours after a meal. The ADA has the easiest target, less than 180 mg/dl (10 mmol/l). The International Diabetes Federation and the World Health Organization recommend a target of less than 160 mg/ dl (8.9 mmol/l). The American Association of Diabetes Educators, the AACE and the American College of Endocrinology have the most aggressive targets, under 140 mg/dl (7.8 mmol/l). Whatever target you accept, you might bear in mind that people who don’t have diabetes seldom have a level of more than 130 mg/dl two hours after a meal. If you check your level after each meal, you will be able to have a lower blood glucose level, a lower A1C, and less chance of complications.
Why Checking Postprandial Glucose Is Important
Checking your blood glucose (sugar) levels at least once a day — many people do it first thing in the morning — should be part of your overall plan for managing type 2 diabetes. You can use results to better decide what you do next, and how to keep your blood sugar levels where you and your doctor want them.
But if you’re only testing your glucose levels once a day, you’re likely missing the full picture. “Postprandial glucose (PPG) levels — meaning ‘sugar after the meal’ — give you and your care team more important information about how the body is able to manage glucose after a meal,” explains endocrinologist Pratima Kumar, MD, an assistant professor of endocrinology at the University of Texas at Austin. “It informs us if the blood glucose has returned to normal after the meal intake.”
The American Diabetes Association recommends checking fasting (before eating) blood sugar levels, and then testing PPG levels one to two hours after a meal. This is especially important if target A1C goals aren’t being met; this blood test helps shows how well your overall diabetes management plan is working.
You might also need to check your blood glucose numbers at other times during the day, or after certain activities.
What Else You Should Know About Postprandial Glucose
“Glucose levels begin to rise about 10 minutes after the start of a meal and peak two hours after a meal,” Dr. Kumar says. “The glucose levels return to pre-meal levels within two to three hours.”
But PPG numbers don’t just change based on what you eat. They’re also affected by how active you are, your insulin sensitivity, and how quickly food moves through your stomach, says Kumar. The ADA recommends that people with type 2 diabetes keep their PPG under 180 mg/dL.
How Knowing Your PPG Can Give You Control Over Your Diabetes
Information on PPG can help you troubleshoot in important ways. When blood sugar spikes after meals, and stays high, it can be hard to get levels back down to where you want them, according to the American Association of Clinical Endocrinologists (AACE). If your A1C continues to be higher than your target goal, your risk for developing complications rises.
“By measuring PPG, we can determine whether dietary modifications or pre-meal bolus insulin is needed to reduce these spikes,” Kumar says. “In patients who achieve their pre-meal glucose targets but whose A1C remains above target, PPG monitoring and therapy is recommended.”
Learning how to count carbohydrates can help you achieve your goals for blood sugar levels after eating.
“Carbohydrates contribute significantly more to PPG than fat and protein content of a meal,” Kumar says. Checking PPG regularly can help you figure out the best balance of carbohydrates, fats, and proteins.
If you’re using insulin, talk to your doctor about what to do if your PPG levels are higher or lower than your goal, the AACE says.
Who Should Check PPG?
How often you should test PPG is based on you specifically, and on your goals for controlling your blood sugar. You should work with your care team to identify your testing regimen and target goals. The ADA does recommend that certain people test PPG and blood sugar levels more frequently, including:
- Pregnant women with gestational diabetes
- Women with type 1 or 2 diabetes who are pregnant
- People trying new insulin or a new insulin dosage
- People with diabetes that’s hard to control
- People with history of high blood sugar after eating
- People who take multiple medications and are at risk for high or low blood sugar
“Blood glucose levels vary at different times throughout the day over a period of weeks,” Kumar says. “Thus, it’s important to check your blood glucose at regular intervals to provide accurate information to your physician.”
How to Test PPG
Blood sugar testing seems simple enough, but there are a few tips that will ensure you get the most accurate numbers:
- Wash your hands before testing. If you have any residue on your hands, such as juice from a fruit you ate, you will be testing that sugar as well.
- Store test supplies correctly. Read the instructions on your supplies, Kumar says, to make sure “their integrity and accuracy isn’t compromised by moisture and heat.”
Additional reporting by Andrea Peirce
post prandial blood sugar test Test
The Postprandial glucose test or PPBS is a glucose test done on the blood that helps determine the type of sugar, also known as glucose after a certain meal. Carbohydrate foods are the main sources of glucose and it is a primary source of energy present in the body.
Blood glucose levels generally increase a bit after eating a meal. It is because the pancreas releases insulin which helps the body remove glucose from the blood and store it as energy. Those suffering from diabetes will not be able to respond to the insulin and this keeps their glucose levels high. The levels remain high and over time, this can cause damage to the eyes, nerves, kidneys and blood vessels as well.
The postprandial test is generally undertaken for two hours and it precisely measures the glucose in the blood two hours after eating a meal. The timing for the same begins from the start of the meal. After 2 hours, blood sugar levels generally drop back to normal for healthier individuals but it can remain high for those with diabetes. It thus serves as a final test for those who may have diabetes and whether the person with diabetes is able to manage his blood sugar levels.
Introduction to Postprandial Blood Sugar
If, you are, diagnosed with diabetes, your doctor must have told you the importance of monitoring your blood sugar levels. A spike in blood glucose level that comes after you eat something is called “postprandial” blood glucose; this sudden rise in sugar levels can be taken care of by following some simple steps, and help avoid health problems.
Why is Postprandial Blood Glucose Important?
The American Diabetes Association (ADA) has recommended that you check your blood sugar levels right before mealtime with a blood sample from a finger stick. Then do it again 1 to 2 hours after that first bite of food.
You need to keep this up for a week or so. Write down the time and the blood sugar number. Make a note about anything you think might affect your levels, like medicine or exercise. And don’t forget to write what you ate, the portion sizes and (if possible) the number of carbs.
A postprandial plasma glucose test is a blood test that measures blood glucose levels following a meal consisting of a set amount of carbohydrate. The tests show how tolerant is your body towards glucose.
How is the Test Performed?
A set amount of glucose is taken orally. According to the IDF (International Diabetes Federation), the blood glucose targets are based on taking 75g of glucose. Following the intake of carbohydrates, a blood test is taken two hours after ingesting the glucose.
When is Diabetes Diagnosed?
The following results of postprandial sugar level are based on the IDF guidelines for diagnosing diabetes.
Other conditions, for example, certain medications or recent illnesses may also affect the results which will be taken into consideration for diagnostic purposes.
Therefore, in such cases, the test may be repeated at a later date.
How Should You Take Care of After-Meal Spikes?
If you’re trying to manage diabetes, you must have been told how do you handle a spike in blood glucose that comes after a meal? Rapid-acting oral insulin secretagogues, rapid-acting insulin analogs, and alpha-glucosidase inhibitors help to reduce postprandial glucose. They also reduce HbA1c, but to what extent HbA1c is lowered is yet to be studied.
Why Should You Keep an Eye on Postprandial Blood Glucose?
When your blood sugar level is high, you can get symptoms like a foggy-headedness. Such symptoms make it hard to concentrate or think clearly. You may feel nervous or mood. Even your energy may also take a dive.
If the sugar level goes too low, that is not healthy either. In the long run, if your blood sugar stays up, you could be at risk for stroke, heart disease, kidney disease, or other physiological problems.
Blood glucose levels vary at different times throughout the day over a period of weeks, as the experts say. Therefore, it’s important to check your blood glucose at regular intervals to provide accurate information to your physician. Wash your hands before testing. Else any residue on your hands, such as juice from a fruit you ate, will affect be test results of that sugar as well.
The 6E Approach to Person-centered Care
Post-prandial blood glucose levels are generally 2 Post-prandial hyperglycemia is defined as a plasma glucose level exceeding 140mg/dl.3 Development of post-prandial hyperglycemia coincides with an impairment or absence of the first-phase insulin response, a decrease in insulin sensitivity in the peripheral tissues, and decreased suppression of hepatic glucose output after meals due to insulin deficiency.4 Post-prandial hyperglycem
Post-prandial blood glucose levels are generally 2 Post-prandial hyperglycemia is defined as a plasma glucose level exceeding 140mg/dl.3 Development of post-prandial hyperglycemia coincides with an impairment or absence of the first-phase insulin response, a decrease in insulin sensitivity in the peripheral tissues, and decreased suppression of hepatic glucose output after meals due to insulin deficiency.4 Post-prandial hyperglycemia is also one of the earliest abnormalities of glucose homeostasis associated with type 2 diabetes, and worsens—progressing to fasting hyperglycemia— as the condition progresses.5 The relative contribution of PPG varies across the day: it is highest at HbA1c levels of ~6.5%, when FPG levels are close to normal, and lowest at HbA1c levels >8%, when the FPG level predominates.6 Thus, a triad model of diabetes management in which all three parameters—HbA1c, PPG, and FPG levels—are considered to be interrelated and therapeutic targets could potentially optimize glycemic control.7
Post-prandial hyperglycemia is common both in patients with diabetes and in those considered to have adequate glycemic control. A US study of individuals with type 2 diabetes found post-challenge glucose values of ≥200mg/dl in nearly 74% of patients.8 Individuals with type 1 diabetes on intensive insulin therapy regimens also show elevations of PPG—levels of 140mg/dl were detected in 77% of one study patient population.9 The Diabetes Control and Complications Trial (DCCT)10,11 and the UK Prospective Diabetes Study (UKPDS)12–14 clearly demonstrated a strong correlation between glycemic control and the incidence of late microvascular and macrovascular complications. Lowering of HbA1c significantly delayed the onset or slowed the progression of diabetic retinopathy, nephropathy, and neuropathy, as well as myocardial infarction (MI). Since PPG has been shown to contribute to HbA1c levels, targeting PPG should help reduce the risk for complications. Several studies have found associations between PPG and cardiovascular risk.15–17 Evidence suggests that acute hyperglycemia may increase cardiovascular risk by a variety of mechanisms at tissue, cellular, and biochemical levels, leading to the generation of oxidative stress.18 Markers of cardiovascular risk have also been associated with elevated PPG levels. The one-hour PPG level has been linked to a rise in carotid intima-media thickness (CIMT), a marker of atherosclerosis.19 PPG has also been linked to inflammation and endothelial dysfunction20,21 and adhesion molecules.22 It has been postulated that acute hyperglycemia, free fatty acids, and insulin resistance cause oxidative stress, protein kinase-C (PKC) activation, and advanced glycated end-product receptor (RAGE) activation, leading to vasoconstriction, inflammation, and thrombosis.23
Post-prandial and post-challenge hyperglycemia is associated with a variety of complications including nephropathy and retinopathy,24 decreased myocardial blood volume/blood flow,25 increased risk for ancer,26–29 and impaired cognitive function in the elderly.30 In MI patients both with and without diabetes, high levels of blood glucose at admission have been associated with an increased risk for death.31
Measurement of Post-prandial Glucose
The oral glucose tolerance test (OGTT) was once widely used as the firstchoice test for the diagnosis of diabetes, gestational diabetes, impaired glucose tolerance, or reactive hypoglycemia. The OGTT involves measurement of baseline fasting plasma glucose, then plasma glucose is measured again at two hours following a glucose ‘challenge.’ Glucose tolerance is defined as normal (NGT), impaired (IGT), or indicative of overt diabetes. The test has the advantage of simplicity; however, it is expensive and not considered physiological because the 75–100g of glucose used in the challenge is rarely consumed during a meal. Since 1997, the American Diabetes Association (ADA) has recommended that FPG testing replace OGTT as the first-choice test for the diagnosis of diabetes or IGT.32 It has been demonstrated, however, that the level of glycemia reached two hours after an OGTT correlates strongly to the level reached after a standardized meal, particularly among those with IGT, suggesting that among this group the two-hour OGTT glucose level provides valuable information on altered carbohydrate metabolism during a meal.33
Findings from two large-scale epidemiological studies—the European DECODE and the Asian DECODA—have shown that serum glucose level at least two hours after oral challenge with glucose is a more powerful predictor of cardiovascular risk than fasting glucose.15,16 Furthermore, a meta-analysis demonstrated a linear increase of cardiovascular risk within a wide range of two-hour plasma glucose values, but demonstrated a threshold effect for fasting plasma glucose values up to ~100mg/dl.17
The two-hour timescale for measurement of PPG/post-challenge glucose is generally used because it is consistent with the guidelines published by most of the leading diabetes organizations and medical associations. However, in recent years a focus on glucose fluctuations has led to the definition of new parameters in the assessment of PPG. It has been demonstrated that a single fluctuation in blood glucose is almost always accompanied by an alteration in endothelial function, and oscillating glucose over 24 hours has been shown to cause more endothelial dysfunction than a stable constant high level of glucose.34 The glucose ‘spike’—i.e. the difference between the baseline glucose level before an OGTT and the ‘peak’ value during an OGTT—has been found to be a more powerful predictor of CIMT in those with IGT than the glycemic peak at two hours, regardless of the time after glucose challenge and the level of FPG.35 The effect of acute glycemia on endothelial function is dependent on glucose concentration, and in diabetic patients this does not depend on the basal level of glycemia already present.34 A recent study of 611 patients with diabetes in normal daily life defined the term incremental glucose peak (IGP) as the maximal incremental increase in blood glucose obtained at any point following a meal, and also showed a correlation with CIMT. Moreover, IGPs tend to occur at the same time: 95% of the diabetic population studied had an IGP occurring within one hour after the start of the meal, and timing was not influenced by diet or drugs. It has been suggested that of the glycemic parameters usually used to identify both chronic and post-prandial hyperglycemia, IGP is the best predictor of CIMT.36
Managing Post-prandial Glucose There is much evidence to suggest that although treatment of type 2 diabetes always carries a risk of hypoglycemia, fears regarding the safety of PPG control have proved unfounded.1 Management of PPG using the short-acting insulin analog aspart reduces oxidative stress and improves arterial function.37 The STOP-NIDMM trial indicated that treatment of patients with IGT with the alpha-glucosidase inhibitor acarbarose, a compound that specifically reduces PPG, causes a reduction in the risk for progression to diabetes, development of hypertension, and cardiovascular events.38,39 Acarbarose treatment has been associated with a significant decrease in CIMT.40
Other agents that affect PPG include the alpha-glucosidase inhibitor miglitol and the rapid-acting insulin secretagogs repaglinide and nateglinide. Diets with a low glycemic load are also beneficial in controlling PPG. Future studies of non-pharmacological and pharmacological therapies should greatly increase our understanding of the relative benefits of pre- and post-prandial glucose as therapeutic targets. In any therapeutic regime, it is important that each therapy be appropriately matched to a patient’s ability to recognize and respond to hypoglycemia when it does occur.
Previous guidelines published by the ADA defined targets for fasting and bedtime glucose levels but not for PPG.41 The International Diabetes Federation’s (IDF’s) guidelines previously defined a level for two-hour PPG of 42 The guideline development group has stated that the goal of diabetes therapy should be to achieve near-normal glycemic status by the safest possible means in all three measures of glycemic control: HbA1c, FPG, and PPG.43 The IDF and other organizations define normal glucose tolerance as The IDF, following an extensive, systematic search of the literature published over the past 20 years, proposed the following recommendations in the IDF Guideline for Management of Postmeal Glucose:42
- post-prandial hyperglycemia is harmful and should be addressed;
- implement treatment strategies to lower post-prandial plasma glucose in people with post-prandial hyperglycemia;
- a variety of both non-pharmacological and pharmacological therapies should be considered to target post-prandial plasma glucose;
- two-hour post-prandial plasma glucose should not exceed 140mg/dl as long as hypoglycemia is avoided;
- self-monitoring of blood glucose (SMBG) should be considered because it is currently the most practical method for monitoring postprandial glycemia; and
- the efficacy of treatment regimens should be monitored as frequently as needed to guide therapy toward achieving post-prandial plasma glucose target.
Following this report, guidelines published by most of the leading diabetes organizations and medical associations have been revised, adding recommendations for PPG. A summary of the various guidelines is given in Table 1. The two-hour timescale for measurement of plasma glucose concentrations is the most commonly recommended. It is the safest timescale for those treated with insulin, particularly if they are inexperienced or have been poorly advised, as they may respond inappropriately to an elevated one-hour plasma glucose level by taking an additional insulin bolus without waiting for the initial bolus to take effect.43 This can lead to severe hypoglycemia.
SMBG is currently considered the optimal method for assessing glucose levels. In contrast to periodic HbA1c testing, which indicates the mean value of blood glucose over the preceding two to three months, SMBG provides immediate feedback to patients regarding glucose levels throughout the day. Both tests are essential for assessing glycemic control, with HbA1c considered the preferred standard for predicting long-term micro- and macrovascular complications. Specific protocols remain variable, however, particularly among non-insulin-using patients.44–49 SMBG can lead to improved glycemia by revealing the immediate effect of patient behavior on blood glucose levels.
Although SMBG is recommended in the daily management of type 1 diabetes and insulin-treated type 2 diabetes, worldwide healthcare guidelines have not generally advised SMBG for non-insulin-using patients. This is due to the high cost of frequent SMBG and the tradition of evaluating SMBG use in terms of HbA1c.49 However, the correlation between glycemic spikes and oxidative stress previously discussed has led to suggestions that all patients with diabetes perform SMBG to monitor glycemic variability.35,50 In a large managed care study, an association between frequent monitoring of blood glucose and clinically and statistically better glycemic control was observed regardless of diabetes type or therapy.51 During pregnancy, regular post-prandial monitoring is accepted, supported by evidence that patients using postprandial glucose goals have improved fetal outcomes.52 It must be remembered that SMBG is only one component of diabetes management, and its benefits require training of patients to perform SMBG, interpret their test results, and appropriately adjust their treatment regimens to achieve glycemic control. Moreover, clinicians should be familiar with interpreting SMBG data, prescribing appropriate medications, and closely monitoring patients in order to make timely adjustments to their regimens as needed.
Table 1: Summary of Post-prandial Glucose Guidelines
On the basis of the new guidelines, it has been recommended that people treated with insulin perform SMBG ≥3 times a day; SMBG frequency for people who are not treated with insulin should be individualized to each person’s treatment regimen and level of glycemic control.43 Given that glycemic status is the sum of the fasting, postprandial, and post-absorptive states, at least one test per day from each of these periods would be ideal. In reality, though, over 65% of patients with non-insulin-treated type 2 diabetes practice SMBG less than once daily, due in part to cost, inadequate patient education, and/or poor patient motivation.53 While these obstacles require long-term solutions, a possible interim measure is to target either FPG or PPG, depending on HbA1c level.
New techniques for glucose monitoring are emerging: these include continuous glucose monitoring (CGM), in which a sensor measures glucose at intervals of up to 10 minutes and transmits this reading to a data storage device.54 Results can be downloaded retrospectively by the physician, or displayed in realtime in the monitor. Markers for postprandial hyperglycemia such as 1,5-anhydroglucitol (1,5-AG), a naturally occurring dietary polyol, have also been studied.55
Post-prandial and post-challenge hyperglycemia are associated with cardiovascular and other risks. The importance of PPG is now widely accepted, and this is reflected in the new guidelines. Strategies that target both FPG and PPG are needed to optimize glycemic control, and treatment of both should be initiated simultaneously at any HbA1c level. Subject to available therapies and technologies, a two-hour PPG 1 It is therefore imperative that healthcare providers find ways to improve their effectiveness in treating hyperglycemia. Although cost will remain an important factor in determining appropriate treatments, controlling glycemia is ultimately much less expensive than treating the complications of diabetes.
Management of Gestational Diabetes Mellitus
Management of Gestational Diabetes
BLOOD GLUCOSE MONITORING
In patients requiring insulin therapy, the ideal frequency of glucose monitoring has not been established. A common practice is to check the glucose level four times daily. A first morning glucose level can rule out fasting hyperglycemia, and additional one- or two-hour postprandial values can ensure adequate control.
Postprandial testing is preferable to preprandial testing. In one randomized study comparing postprandial and preprandial blood glucose monitoring in patients with gestational diabetes who required insulin therapy, those who measured their glucose levels after meals had larger drops in A1c (−3.0 versus −0.6 percent, P <.001), gave birth to infants with lower birth weights (3,469 g versus 3,848 g , P = .01), and had fewer cesarean deliveries (12 versus 42 percent, P = .04).19
There is neither objective evidence nor a clinical guideline to support a frequency for glucose monitoring in patients with diet-controlled gestational diabetes. In these patients, an acceptable practice is to use the four-times-a-day schedule on two days per week and begin more intensive treatment if two values per week exceed the limits.
A recent Cochrane review20 found no difference in the prevalence of birth weights greater than 4,000 g (8 lb, 13 oz) or cesarean deliveries in women with gestational diabetes who were randomly assigned to receive primary dietary therapy or no specific treatment. The review concluded that insufficient evidence exists to recommend dietary therapy in patients with altered glucose metabolism.
The ideal diet for women with gestational diabetes remains to be defined, and current recommendations are based on expert opinion.14 The ADA recommends nutrition counseling (with a registered dietitian, if possible) and a diet that adequately meets the needs of pregnancy but restricts carbohydrates to 35 to 40 percent of daily calories. Caloric restriction should be approached with caution, because two studies have reported a relationship between elevated maternal serum ketone levels and reduced psychomotor development and IQ at three to nine years of age in the offspring of mothers with gestational diabetes.21,22
For patients with a body mass index greater than 30 kg per m2, the ADA suggests lowering daily caloric intake by 30 to 33 percent (to approximately 25 kcal per kg of actual weight per day), which avoids ketonemia. Regular exercise has been shown to improve glycemic control in women with gestational diabetes, but it has not been shown to affect perinatal outcomes.23 (For additional dietary recommendations, see the accompanying patient information handout.)
Most,24–26 but not all,27,28 prospective trials involving insulin therapy in women with gestational diabetes have shown a reduction in the incidence of neonatal macrosomia. Therefore, insulin therapy traditionally has been started when capillary blood glucose levels exceed 105 mg per dL (5.8 mmol per L) in the fasting state and 120 mg per dL (6.7 mmol per L) two hours after meals. These cutoff values are derived from guidelines for managing insulin in pregnant women who have type 1 diabetes. A more aggressive goal of a fasting capillary blood glucose level below 95 mg per dL (5.3 mmol per L) is supported by a prospective study of 471 women with gestational diabetes that showed a decrease in large-for-gestational-age neonates, from 28.6 to 10.3 percent (relative risk, 5.99; 95 percent confidence interval, 1.37 to 8.88), in the women with fasting blood glucose levels of 95 to 105 mg per dL who were treated, respectively, with diet or insulin; the study reported no data on additional birth outcomes.29 This more conservative goal is recommended in the most recent ACOG practice bulletin on gestational diabetes.15 Because of variable and imperfect data on this point, it is acceptable to use either cutoff value for fasting glucose testing.
One prospective nonrandomized study of 445 patients has shown a reduction in operative deliveries and birth trauma in women with gestational diabetes who are treated with insulin.30 However, the findings of this study remain to be demonstrated in an adequately powered RCT.
There are no specific studies declaring one type of insulin or a certain regimen as superior in affecting any perinatal outcome. A common initial dosage is 0.7 units per kg per day, with one dose consisting of two thirds of the total amount given in the morning and one dose consisting of one third of the total amount given in the evening. One third of each dose is given as regular insulin, and the remaining two thirds as NPH insulin. A recent study of 42 women with gestational diabetes supports the safety of very-short-acting insulin lispro, which can be used with once-daily extended insulin ultralente.31 The simplest regimen that will control blood glucose levels is the best.
Physicians should expect to increase the insulin dosage as the pregnancy progresses and insulin resistance increases. No published guidelines are available to help family physicians treat patients with gestational diabetes who require insulin. When necessary, collaborative care with an obstetrician or perinatologist is advisable.
ORAL HYPOGLYCEMIC MEDICATIONS
Use of oral hypoglycemic agents to treat gestational diabetes has not been recommended because of concerns about potential teratogenicity and transport of glucose across the placenta (causing prolonged neonatal hypoglycemia).32 Although first-generation hypoglycemic agents (chlorpropamide , tolbutamide ) have been shown to cross the placenta, recent in vitro and in vivo evidence has determined that glyburide (Micronase) does not enter the fetal circulation.33,34
A recent RCT comparing the use of glyburide and insulin in women with gestational diabetes demonstrated that glyburide therapy resulted in comparable maternal outcomes (e.g., glycemic control, cesarean deliveries) and neonatal outcomes (e.g., macrosomia, hypoglycemia, intensive care unit admissions). Glyburide therapy was not started before 11 weeks of gestation and was not detected in any of the neonatal cord blood samples. Preliminary evidence from this trial suggests that glyburide may be a safe, effective alternative to insulin in the management of gestational diabetes.
The ACOG15 and the ADA20 agree that glyburide should not be prescribed for the treatment of gestational diabetes until additional RCTs support its safety and effectiveness. Despite these recommendations, many physicians are using glyburide in this setting because of its ease of use compared with insulin. In a recent prospective cohort study of patients with polycystic ovary syndrome,33 metformin therapy has been shown to decrease the subsequent incidence of gestational diabetes, reduce first-trimester miscarriage rates, and result in no apparent increase in congenital anomalies.35 RCTs are needed to demonstrate the safety and effectiveness of metformin (Glucophage) in pregnancy before use of this medication is warranted for the treatment of gestational diabetes.
ANTEPARTUM FETAL ASSESSMENT
Data on gestational diabetes and an increased risk of fetal demise are conflicting. The 2001 ACOG practice bulletin15 concludes that evidence is insufficient to determine the optimal antepartum testing regimen in women with gestational diabetes who have relatively normal glucose levels on diet therapy and no other perinatal risk factors. Acceptable practice patterns for monitoring pregnancies complicated by gestational diabetes range from testing all women beginning at 32 weeks of gestation to no testing until 40 weeks of gestation.
The ACOG15 recommends antenatal testing for patients whose blood glucose levels are not well controlled, who require insulin therapy, or who have concomitant hypertension. The antenatal testing can be initiated at 32 weeks of gestation. In this situation, no method of antenatal testing has proved superior to others. Community preference may dictate use of the nonstress test, the modified biophysical profile (i.e., nonstress test and amniotic fluid index), or a full biophysical profile.
TIMING AND ROUTE OF DELIVERY
In gestational diabetes, shoulder dystocia is the complication most anticipated at the time of delivery. In one study,36 this complication occurred in 31 percent of neonates weighing more than 4,000 g who were delivered vaginally to unclassified mothers with diabetes. No prospective data support the use of cesarean delivery to avoid birth trauma in women who have gestational diabetes. One remaining limiting factor is the 13 percent error rate (± 2 SD) in estimating fetal weight by ultrasonography.37
A decision analysis38 that evaluated the cost and efficacy of a policy of elective cesarean delivery for an estimated fetal weight of 4,500 g (9 lb, 15 oz) in mothers with diabetes found that 443 cesarean deliveries would need to be performed to prevent one case of brachial plexus injury, at a cost of $930,000. A reasonable approach is to offer elective cesarean delivery to the patient with gestational diabetes and an estimated fetal weight of 4,500 g or more, based on the patient’s history and pelvimetry, and the patient and physician’s discussion about the risks and benefits. There are no indications to pursue delivery before 40 weeks of gestation in patients with good glycemic control unless other maternal or fetal indications are present.
The goal of intrapartum management is to maintain normoglycemia in an effort to prevent neonatal hypoglycemia. Patients with diet-controlled diabetes will not require intrapartum insulin and simply may need to have their glucose level checked on admission for labor and delivery. While patients with insulin-requiring diabetes are in active labor, capillary blood glucose levels should be monitored hourly. Target values are 80 to 110 mg per dL (4.4 to 6.1 mmol per L).39
Women with gestational diabetes rarely require insulin in the postpartum period. As insulin resistance quickly resolves, so does the need for insulin. Patients with diet-controlled diabetes do not need to have their glucose levels checked after delivery. In patients who required insulin therapy during pregnancy, it is reasonable to check fasting and two-hour postprandial glucose levels before hospital discharge.
Because women with gestational diabetes are at high risk for developing type 2 diabetes in the future, they should be tested for diabetes six weeks after delivery via fasting blood glucose measurements on two occasions or a two-hour oral 75-g glucose tolerance test. Normal values for a two-hour glucose tolerance test are less than 140 mg per dL. Values between 140 and 200 mg per dL (11.1 mmol per L) represent impaired glucose tolerance, and greater than 200 mg per dL are diagnostic of diabetes. Screening for diabetes should be repeated annually thereafter, especially in patients who had elevated fasting blood glucose levels during pregnancy.40
Breastfeeding improves glycemic control and should be encouraged in women who had gestational diabetes.41
Contraception should be discussed, because women who have diabetes during one pregnancy are likely to have the same condition in a subsequent pregnancy. There are no limits on the use of hormonal contraception in patients with a history of gestational diabetes. As previously noted, these women also are at increased risk of developing type 2 diabetes in the future.
Patients should be counseled about diet and exercise. By losing weight and exercising, women can significantly decrease their risk of developing diabetes.