Diabetes in pregnancy: clinical approach
文摘
科学
2024-07-31 07:00
澳大利亚
If you would like to view past exciting content, please click on the following link.Diabetes is one of the most common medical complications during pregnancy. Pregnant patients with diabetes are more likely to develop preeclampsia and require cesarean delivery. Elevated glucose levels cross the placenta, resulting in an increased glucose supply to the fetus. The fetal pancreas responds by producing more insulin to manage the excess glucose. Fetal hyperinsulinemia leads to increased fat accumulation, particularly in the shoulders and chest, causing macrosomia, shoulder dystocia, and birth trauma.Furthermore, once the umbilical cord is clamped after delivery, the maternal glucose supply is interrupted, potentially leading to neonatal hypoglycemia. Most cases of diabetes in pregnancy are gestational diabetes mellitus (GDM), which is hyperglycemia that develops during pregnancy. However, many patients do not undergo diabetes screening before pregnancy, making it challenging to distinguish between GDM and preexisting type 1 or type 2 diabetes.The initial step in evaluating a patient for diabetes screening in pregnancy is to obtain a focused history and physical exam, ideally at the start of prenatal care. It is essential to determine if a patient has a prior diagnosis of type 1 or type 2 diabetes, which indicates pregestational diabetes mellitus. This distinction is crucial, as patients with pregestational diabetes are more likely to experience significant maternal and fetal complications and usually require additional monitoring.If the patient has no prior diagnosis of type 1 or type 2 diabetes, the next step is to assess their risk for GDM. High-risk patients typically have an elevated BMI of at least 25, or at least 23 in patients of Asian descent, along with one or more additional risk factors. These risk factors include a history of GDM in a previous pregnancy, a first-degree relative with diabetes, a previous delivery of an infant weighing at least 4,000 grams (approximately 9 pounds), or a personal history of polycystic ovarian syndrome or cardiovascular disease.Additional risk factors can be identified during a physical examination, such as hypertension or prepregnancy morbid obesity with a BMI greater than 40. Laboratory-related risk factors include a hemoglobin A1c of 5.7% or greater and certain abnormal lipid values, such as an HDL lower than 35 mg/dL and triglycerides higher than 250 mg/dL.All pregnant patients should be screened for GDM, with the timing based on their risk factors. Average-risk patients, who have no additional risk factors for GDM, are screened at 24 to 28 weeks of gestation using a 50-gram, one-hour oral glucose tolerance test. A normal test result indicates that the patient does not have gestational diabetes and can continue with routine prenatal care.A clinical note: The cut-off value for a normal one-hour glucose test varies between 130 and 140 mg/dL because there is insufficient evidence to determine the ideal threshold for GDM screening. Each clinical site or institution should decide on a consistent cut-off value for their practice.Regardless of the screening cut-off used, if the one-hour glucose test for an average-risk patient is elevated, the patient should undergo a 100-gram, three-hour oral glucose tolerance test. This test includes a fasting glucose measurement and additional measurements at 1, 2, and 3 hours after consuming the glucose load.Here’s a high-yield fact! A commonly used set of diagnostic thresholds for the three-hour glucose test is the Carpenter and Coustan criteria, which include normal glucose values of fasting below 95, a one-hour result below 180, a two-hour result below 155, and a three-hour result below 140. Another acceptable approach is to use the glucose values established by the National Diabetes Data Group: fasting less than 105, one-hour less than 190, two-hour less than 165, and three-hour less than 145.Returning to our patient, the three-hour test is considered normal if no more than one of the four values is elevated. A normal three-hour test result at 24 to 28 weeks indicates that the patient does not have gestational diabetes and can resume routine prenatal care.Here’s another clinical pearl! Patients with only one elevated value on a three-hour glucose tolerance test are considered to have a normal result but are diagnosed with impaired glucose tolerance. This condition significantly increases the risk of adverse pregnancy outcomes, including neonatal macrosomia, compared to those with no abnormal values, and may warrant closer observation.If the three-hour glucose tolerance test shows two or more elevated glucose measurements, the result is abnormal, and the patient is diagnosed with gestational diabetes.Another quick clinical pearl! There is also a one-step 75-gram glucose tolerance test that serves both screening and diagnostic purposes, but it is less preferred compared to the two-step 50- and 100-gram tests.Before we move on to classification, let’s discuss high-risk patients for GDM. These patients should undergo screening at the initiation of prenatal care with an early one-hour oral glucose tolerance test. If the early one-hour glucose test is normal, they can return to routine average-risk GDM screening at 24 to 28 weeks. However, if the early one-hour glucose test is elevated, the patient should proceed with an early three-hour oral glucose tolerance test. An abnormal early three-hour test indicates gestational diabetes.If the patient has a normal early three-hour oral glucose tolerance test, they should be retested at 24 to 28 weeks. However, you can skip the one-hour test at that time, as patients with an abnormal early one-hour glucose screen are likely to have an abnormal one-hour screen later in pregnancy. Proceed directly to the three-hour test at 24 to 28 weeks. If it’s abnormal, the patient has developed gestational diabetes. If it’s normal, they can continue routine prenatal care.Here’s a clinical pearl! Previously, diagnosing diabetes at any point in pregnancy was considered GDM, even though some of these patients actually had pregestational diabetes. Today, if diabetes is identified in the first trimester or early second trimester using standard diagnostic criteria—hemoglobin A1c of 6.5% or greater, fasting glucose of 126 or greater, or a 2-hour glucose of 200 or greater on a 75-gram oral glucose tolerance test—pregestational diabetes is diagnosed.Once gestational diabetes mellitus (GDM) is diagnosed, patients should receive education on lifestyle modifications, including nutritional counseling for a carbohydrate-controlled diet and safe, regular exercise. Patients should also learn to check fasting and postprandial (after-meal) fingerstick glucose levels daily to monitor glucose control. Target glucose levels include fasting glucose less than 95 mg/dL and either one-hour postprandial glucose less than 140 mg/dL or two-hour postprandial glucose less than 120 mg/dL. Clinicians typically review a patient’s glucose levels every one to two weeks.Patients who consistently achieve target glucose levels with diet and exercise alone are classified as A1GDM and can continue their current management. Those unable to achieve target glucose levels consistently have A2GDM and require a combination of diet, exercise, and medication for optimal management. Pharmacotherapy, typically insulin, should be added to achieve adequate glucose control. Metformin is a reasonable second-line choice for patients who decline, cannot afford, or are unable to safely administer insulin.Diabetes mellitus is a common medical complication of pregnancy. Some patients enter pregnancy with a previous diagnosis of type 1 or type 2 diabetes, known as pregestational diabetes. However, most cases of diabetes during pregnancy are diagnosed through early or routine glucose screening for gestational diabetes mellitus (GDM). Patients at average risk for GDM are screened between 24 and 28 weeks of gestation. Those at high risk for GDM should begin screening at the start of prenatal care. Individuals diagnosed with GDM should receive education on a carbohydrate-controlled diet, safe regular exercise, and how to check fasting and postprandial glucose levels. Patients who can control their glucose levels through lifestyle modifications have A1GDM. If they cannot consistently achieve target glucose levels after lifestyle changes, they have A2GDM and require pharmacotherapy for management. - - - - - - - END - - - - - - -
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